As most of you guys know my gf2mx400 is dead

After a month using a crappy 2mb pci card I've borrowed a V3 3k agp from a friend

After uninstalling the old drivers I've set up the card, installed the card drivers, the via 4in1 drivers but, after rebooting the system locked-up just after the desktop showed up

Sometimes the desktop doesn't even appear, just a black screen
What should I do?