C´est peut être un problème de voltage!
Un extrait du support technique de ta carte mère dans la section video:
" What add-in AGP cards can be used?
The D845EPT2 AGP socket can accept universal AGP cards that comply with the AGP 2.0 specification. The D845EPT2 can use 1X / 2X / 4X card(s) operating at 1.5V.
Note: Legacy 3.3V AGP cards are not supported."
http://www.intel.com/design/motherbd/pt2/pt2_inst.htm#14.0