je ne sais pas ce qu'à fait mon cousin avec le pc mais il ne démarre plus sauf en mode sans échec (ya un écran noir après le chargement de Windows XP pro, on y voit juste le curseur de la souris). Voici le log HijackThis:

Logfile of Trend Micro HijackThis v2.0.2
Scan saved at 20:14:57, on 06/04/2008
Platform: Windows XP SP2 (WinNT 5.01.2600)
MSIE: Internet Explorer v6.00 SP2 (6.00.2900.2180)
Boot mode: Safe mode with network support

Running processes:
C:\WINDOWS\System32\smss.exe
C:\WINDOWS\system32\winlogon.exe
C:\WINDOWS\system32\services.exe
C:\WINDOWS\system32\lsass.exe
C:\WINDOWS\system32\svchost.exe
C:\WINDOWS\system32\svchost.exe
C:\WINDOWS\Explorer.EXE
C:\Program Files\Trend Micro\HijackThis\HijackThis.exe

R0 - HKCU\Software\Microsoft\Internet Explorer\Main,Start Page = http://go.microsoft.com/fwlink/?LinkId=69157
R1 -
HKCU\Software\Microsoft\Windows\CurrentVersion\Int
ernet Settings,ProxyServer = http=localhost:8118;https=localhost:8118
R0 - HKCU\Software\Microsoft\Internet Explorer\Toolbar,LinksFolderName = Liens
O2 - BHO: Adobe PDF Reader Link Helper - {06849E9F-C8D7-4D59-B87D-784B7D6BE0B3} - C:\Program Files\Adobe\Acrobat 7.0\ActiveX\AcroIEHelper.dll
O2 - BHO: flashget urlcatch - {2F364306-AA45-47B5-9F9D-39A8B94E7EF7} - C:\Program Files\FlashGet\jccatch.dll
O2 - BHO: NCardAPP - {305839F2-5982-4095-9845-50024E5A2F78} - (no file)
O2 - BHO: SSVHelper Class - {761497BB-D6F0-462C-B6EB-D4DAF1D92D43} - C:\Program Files\Java\jre1.6.0_01\bin\ssv.dll
O2 - BHO: (no name) - {7E853D72-626A-48EC-A868-BA8D5E23E045} - (no file)
O2 - BHO: Programme d'aide de l'Assistant de connexion Windows Live - {9030D464-4C02-4ABF-8ECC-5164760863C6} - C:\Program Files\Fichiers communs\Microsoft Shared\Windows Live\WindowsLiveLogin.dll
O2 - BHO: Windows Live Toolbar Helper - {BDBD1DAD-C946-4A17-ADC1-64B5B4FF55D0} - C:\Program Files\Windows Live Toolbar\msntb.dll
O2 - BHO: FlashGet GetFlash Class - {F156768E-81EF-470C-9057-481BA8380DBA} - C:\Program Files\FlashGet\getflash.dll
O3 - Toolbar: Windows Live Toolbar - {BDAD1DAD-C946-4A17-ADC1-64B5B4FF55D0} - C:\Program Files\Windows Live Toolbar\msntb.dll
O4 - HKLM\..\Run: [avgnt] "C:\Program Files\Avira\AntiVir PersonalEdition Classic\avgnt.exe" /min
O4 - HKLM\..\Run: [COMODO Firewall Pro] "C:\Program Files\COMODO\Firewall\cfp.exe" -h
O8 - Extra context menu item: &Tout télécharger avec FlashGet - C:\Program Files\FlashGet\jc_all.htm
O8 - Extra context menu item: &Télécharger avec FlashGet - C:\Program Files\FlashGet\jc_link.htm
O8 - Extra context menu item: &Windows Live Search - res://C:\Program Files\Windows Live Toolbar\msntb.dll/search.htm
O8 - Extra context menu item: Add to Windows &Live Favorites - http://favorites.live.com/quickadd.aspx
O9 - Extra button: (no name) - {08B0E5C0-4FCB-11CF-AAA5-00401C608501} - C:\Program Files\Java\jre1.6.0_01\bin\npjpi160_01.dll
O9 - Extra 'Tools' menuitem: Console Java (Sun) - {08B0E5C0-4FCB-11CF-AAA5-00401C608501} - C:\Program Files\Java\jre1.6.0_01\bin\npjpi160_01.dll
O9 - Extra button: Ajout Direct - {219C3416-8CB2-491a-A3C7-D9FCDDC9D600} - C:\Program Files\Windows Live\Writer\WriterBrowserExtension.dll
O9 - Extra 'Tools' menuitem: &Ajout Direct dans Windows Live Writer - {219C3416-8CB2-491a-A3C7-D9FCDDC9D600} - C:\Program Files\Windows Live\Writer\WriterBrowserExtension.dll
O9 - Extra button: FlashGet - {D6E814A0-E0C5-11d4-8D29-0050BA6940E3} - C:\Program Files\FlashGet\FlashGet.exe
O9 - Extra 'Tools' menuitem: FlashGet - {D6E814A0-E0C5-11d4-8D29-0050BA6940E3} - C:\Program Files\FlashGet\FlashGet.exe
O9 - Extra button: Messenger - {FB5F1910-F110-11d2-BB9E-00C04F795683} - C:\Program Files\Messenger\msmsgs.exe
O9 - Extra 'Tools' menuitem: Windows Messenger - {FB5F1910-F110-11d2-BB9E-00C04F795683} - C:\Program Files\Messenger\msmsgs.exe
O16 - DPF: {20A60F0D-9AFA-4515-A0FD-83BD84642501} (Checkers Class) - http://messenger.zone.msn.com/binary/msgrchkr.cab56986.cab
O16 - DPF: {4F1E5B1A-2A80-42CA-8532-2D05CB959537} (MSN Photo Upload Tool) - http://gfx1.hotmail.com/mail/w2/pr02/resources/MSNPUpld.cab
O16 - DPF: {5D6F45B3-9043-443D-A792-115447494D24} (UnoCtrl Class) - http://messenger.zone.msn.com/FR-FR/a-UNO1/GAME_UNO1.cab
O16 - DPF: {9122D757-5A4F-4768-82C5-B4171D8556A7} (PhotoPickConvert Class) - http://appdirectory.messenger.msn.com/AppDirectory/P4Apps/PhotoSwap/PhtPkMSN.cab
O16 - DPF: {B8BE5E93-A60C-4D26-A2DC-220313175592} (MSN Games - Installer) - http://messenger.zone.msn.com/binary/ZIntro.cab56649.cab
O16 - DPF: {C3F79A2B-B9B4-4A66-B012-3EE46475B072} (MessengerStatsClient Class) - http://messenger.zone.msn.com/binary/MessengerStatsPAClient.cab56907.cab
O16 - DPF: {E6187999-9FEC-46A1-A20F-F4CA977D5643} (ZoneChess Object) - http://messenger.zone.msn.com/binary/Chess.cab57176.cab
O16 - DPF: {F8C5C0F1-D884-43EB-A5A0-9E1C4A102FA8} (GoPetsWeb Control) - https://secure.gopetslive.com/dev/GoPetsWeb.cab
O20 - AppInit_DLLs: C:\WINDOWS\system32\guard32.dll
O23 - Service: AntiVir PersonalEdition Classic Scheduler (AntiVirScheduler) - Avira GmbH - C:\Program Files\Avira\AntiVir PersonalEdition Classic\sched.exe
O23 - Service: AntiVir PersonalEdition Classic Guard (AntiVirService) - Avira GmbH - C:\Program Files\Avira\AntiVir PersonalEdition Classic\avguard.exe
O23 - Service: Apple Mobile Device - Apple, Inc. - C:\Program Files\Fichiers communs\Apple\Mobile Device Support\bin\AppleMobileDeviceService.exe
O23 - Service: COMODO Firewall Pro Helper Service (cmdAgent) - COMODO - C:\Program Files\COMODO\Firewall\cmdagent.exe
O23 - Service: InstallDriver Table Manager (IDriverT) - Macrovision Corporation - C:\Program Files\Fichiers communs\InstallShield\Driver\1150\Intel 32\IDriverT.exe
O23 - Service: Service de l'iPod (iPod Service) - Apple Inc. - C:\Program Files\iPod\bin\iPodService.exe
O23 - Service: MSCSPTISRV - Sony Corporation - C:\Program Files\Fichiers communs\Sony Shared\AVLib\MSCSPTISRV.exe
O23 - Service: PACSPTISVR - Unknown owner - C:\Program Files\Fichiers communs\Sony Shared\AVLib\PACSPTISVR.exe
O23 - Service: SonicStage Back-End Service - Sony Corporation - C:\Program Files\Fichiers communs\Sony Shared\AVLib\SsBeSvc.exe
O23 - Service: Sony SPTI Service (SPTISRV) - Sony Corporation - C:\Program Files\Fichiers communs\Sony Shared\AVLib\SPTISRV.exe
O23 - Service: SonicStage SCSI Service (SSScsiSV) - Sony Corporation - C:\Program Files\Fichiers communs\Sony Shared\AVLib\SSScsiSV.exe

--
End of file - 6238 bytes

de m'aider

'est le log en mode sans eche c? si c'est le cas alors ca ne sert pas a grand chose !

Essaye une restauration systeme a une date anterieur !

J'ai fait un démarrage en mode "sans échec + prise en charge réseau" et je n'arrive pas à mettre à jour AntiVir ou MalwareByte's Malware (mais j'ai accès à Internet)

La "restauration du système" ne fonctionne pas en mode sans échec... je ne sais pas quoi faire...

J'ai fait un scan avec AntiVir et il a trouvé un virus "Trojan horse TR/Dldr.Agent.kht.2" et 7 warning.
Ce que je ne comprends pas c'est comment le virus a réussi à s'installer sur le PC puisqu'il a été réglé sur "protection maximale" (réglé sur scan "all files + archive").

Voici le log:

AntiVir PersonalEdition Classic
Report file date: dimanche 6 avril 2008 20:19

Scanning for 1181183 virus strains and unwanted programs.

Licensed to: Avira AntiVir PersonalEdition Classic
Serial number: 0000149996-ADJIE-0001
Platform: Windows XP
Windows version: (Service Pack 2) [5.1.2600]
Username: user
Computer name: UNICORNI-809C30

Version information:
BUILD.DAT : 270 15603 Bytes 19/09/2007 13:32:00
AVSCAN.EXE : 7.0.6.1 290856 Bytes 23/08/2007 13:16:29
AVSCAN.DLL : 7.0.6.0 49192 Bytes 16/08/2007 12:23:51
LUKE.DLL : 7.0.5.3 147496 Bytes 14/08/2007 15:32:47
LUKERES.DLL : 7.0.6.1 10280 Bytes 21/08/2007 12:35:20
ANTIVIR0.VDF : 6.40.0.0 11030528 Bytes 18/07/2007 14:27:15
ANTIVIR1.VDF : 7.0.3.2 5447168 Bytes 07/03/2008 20:50:31
ANTIVIR2.VDF : 7.0.3.85 434176 Bytes 27/03/2008 20:54:33
ANTIVIR3.VDF : 7.0.3.121 189952 Bytes 04/04/2008 19:49:23
AVEWIN32.DLL : 7.6.0.81 3424768 Bytes 04/04/2008 19:49:23
AVWINLL.DLL : 1.0.0.7 14376 Bytes 26/02/2007 10:36:26
AVPREF.DLL : 7.0.2.2 25640 Bytes 18/07/2007 07:39:17
AVREP.DLL : 7.0.0.1 155688 Bytes 16/04/2007 13:16:24
AVPACK32.DLL : 7.6.0.3 360488 Bytes 15/03/2008 20:50:32
AVREG.DLL : 7.0.1.6 30760 Bytes 18/07/2007 07:17:06
AVARKT.DLL : 1.0.0.20 278568 Bytes 28/08/2007 12:26:33
AVEVTLOG.DLL : 7.0.0.20 86056 Bytes 18/07/2007 07:10:18
NETNT.DLL : 7.0.0.0 7720 Bytes 08/03/2007 11:09:42
RCIMAGE.DLL : 7.0.1.30 2342952 Bytes 07/08/2007 12:38:13
RCTEXT.DLL : 7.0.62.0 86056 Bytes 21/08/2007 12:50:37
SQLITE3.DLL : 3.3.17.1 339968 Bytes 23/07/2007 09:37:21

Configuration settings for the scan:
Jobname..........................: Local Drives
Configuration file...............: c:\program files\avira\antivir personaledition classic\alldrives.avp
Logging..........................: low
Primary action...................: repair
Secondary action.................: delete
Scan master boot sector..........: on
Scan boot sector.................: on
Boot sectors.....................: G:,
Scan memory......................: on
Process scan.....................: on
Scan registry....................: on
Search for rootkits..............: on
Scan all files...................: All files
Scan archives....................: on
Recursion depth..................: off
Smart extensions.................: off
Deviating archive types..........: +BSD Mailbox, +Netscape/Mozilla Mailbox, +Eudora Mailbox, +Squid cache, +Pegasus Mailbox, +MS Outlook Mailbox,
Macro heuristic..................: on
File heuristic...................: medium
Deviating risk categories........: +APPL,+GAME,+JOKE,+PCK,+SPR,

Start of the scan: dimanche 6 avril 2008 20:19

Starting search for hidden objects.
The driver could not be initialized.

The scan of running processes will be started
Scan process 'avscan.exe' - '1' Module(s) have been scanned
Scan process 'avcenter.exe' - '1' Module(s) have been scanned
Scan process 'explorer.exe' - '1' Module(s) have been scanned
Scan process 'svchost.exe' - '1' Module(s) have been scanned
Scan process 'svchost.exe' - '1' Module(s) have been scanned
Scan process 'svchost.exe' - '1' Module(s) have been scanned
Scan process 'svchost.exe' - '1' Module(s) have been scanned
Scan process 'svchost.exe' - '1' Module(s) have been scanned
Scan process 'lsass.exe' - '1' Module(s) have been scanned
Scan process 'services.exe' - '1' Module(s) have been scanned
Scan process 'winlogon.exe' - '1' Module(s) have been scanned
Scan process 'csrss.exe' - '1' Module(s) have been scanned
Scan process 'smss.exe' - '1' Module(s) have been scanned
13 processes with 13 modules were scanned

Starting master boot sector scan:
Master boot sector HD0
[NOTE] No virus was found!
Master boot sector HD1
[NOTE] No virus was found!

Start scanning boot sectors:
Boot sector 'C:\'
[NOTE] No virus was found!
Boot sector 'D:\'
[NOTE] No virus was found!
Boot sector 'E:\'
[NOTE] No virus was found!
Boot sector 'A:\'
[NOTE] In the drive 'A:\' no data medium is inserted!

Starting to scan the registry.
The registry was scanned ( '18' files ).

Starting the file scan:

Begin scan in 'C:\'
C:\pagefile.sys
[WARNING] The file could not be opened!
C:\Documents and Settings\LocalService\NTUSER.DAT
[0] Archive type: TNEF (Microsoft)
[WARNING] Error opening the file
C:\Documents and Settings\LocalService\Local Settings\Application Data\Microsoft\Windows\UsrClass.dat
[0] Archive type: TNEF (Microsoft)
[WARNING] Error opening the file
C:\Documents and Settings\NetworkService\NTUSER.DAT
[0] Archive type: TNEF (Microsoft)
[WARNING] Error opening the file
C:\Documents and Settings\NetworkService\Local Settings\Application Data\Microsoft\Windows\UsrClass.dat
[0] Archive type: TNEF (Microsoft)
[WARNING] Error opening the file
C:\Documents and Settings\user\NTUSER.DAT
[0] Archive type: TNEF (Microsoft)
[WARNING] Error opening the file
C:\Documents and Settings\user\Local Settings\Application Data\Microsoft\Windows\UsrClass.dat
[0] Archive type: TNEF (Microsoft)
[WARNING] Error opening the file
C:\WINDOWS\system32\msfont.dll
[DETECTION] Is the Trojan horse TR/Dldr.Agent.kht.2
[INFO] The file was deleted!
Begin scan in 'D:\'
Begin scan in 'E:\'
Begin scan in 'A:\'
Search path A:\ could not be opened!
Le périphérique n'est pas prêt.

Begin scan in 'F:\'
Search path F:\ could not be opened!
Le périphérique n'est pas prêt.

Begin scan in 'G:\'
Search path G:\ could not be opened!
Le périphérique n'est pas prêt.

End of the scan: dimanche 6 avril 2008 20:44
Used time: 25:10 min

The scan has been done completely.

5116 Scanning directories
74419 Files were scanned
1 viruses and/or unwanted programs were found
0 Files were classified as suspicious:
1 files were deleted
0 files were repaired
0 files were moved to quarantine
0 files were renamed
1 Files cannot be scanned
74418 Files not concerned
3571 Archives were scanned
7 Warnings
0 Notes

J'espère qu'il va démarrer normalement maintenant.