Display Malfunction

Hello. I just replaced a power supply on a Windows XP computer and when it boots up, the os loads just fine, the startup programs begin to load and during this the display settings automatically change from 800x600 32-bit color to 640x480 8-bit color. It has a GeForce 440 MX card and all the drivers and such are working fine. I've tried everything fix it, but am having a less than fun time. Any suggestions would be great.

 

is the power supply big and good enough
in the device manager uninstall the card
reboot tapping f8
from the options choose vga mode
when windows finishes booting
disable a/virus
install the drivers
reboot the computer
if the problem is still there i would suspect the supply is not supplying enough power