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If the full path to this program as shown in The Ultimate Troubleshooter is not C:\WinNT\System32\LSASS.exe ( Windows 2000) or C:\Windows\System32\LSASS.exe ( Windows XP, 2003), then you have the W32.Nimos.Worm virus or some other virus.
Recommendation :
Make sure you have up to date reputable antivirus software and then reboot your PC into Safe Mode and run a full virus scan.