Dumping physical memory

Bonjour,
depuis quelques temps, apres le changement de ma carte graphique j'ai un ecran bleu qui apparait, qui est suivi d'un reboot pc.
Voila ce que me dit l'ecran bleu en question :

A problem has been detected and windows has been shut down to prevent damage to your computer.

If this is the first time you've seen this stop error system, restart your computer.
If this screen appears again, follow these steps :

Check to be sure you have adequate disk space.If a driver is identified in the stop message, disable the driver or check
with the manufacturer for driver updates. Try changing video adapters.

Check with your hardware vendor for any BIOS updates. Disable BIOS memory options such as caching or shadowing.
If you need to use safe mode to remove or disable components, restart your computer, press F8 to select
Advanced startup options, and then select Safe mode.

Technical information :

STOP : 0X0000007E (0X0000005, 0X8A57B859, 0X992DCBB0, 0X992DC8AC)

USBPORT.SYS - Adress 8A57B859 base at 8A554000, Datestamp 47919053

Collecting data for crash dump ...
Initializing disk for crash dump ...
Physical memory dump complete.

Pour le peu que j'ai su comprendre, j'ai changer ma ram je suis passer a 4go, probleme non resolu.
Mon disque dur dispose de 80 Go libre.

Ma config :

Amd athlon 64 X2 Dual Core Processor 4600+ 2.41Ghz
Geforce 9600 Gt (1go) de chez Msi.

Un collegue ayant le meme probleme mais plus rarement a changé son alim pour une plus puissante (480 w la mienne) son pb n'a pas etait resolu.
Merci d'avance pour vos reponses .