Vista help needed can't install

Hello,
I recently purchased windows vista enterprise edition (32-bit ultimate) from a university store. This is only an upgrade version (I can't use a clean install.) So, I installed xp (32 bit professional w/ SP2), and downloaded all of the updates.

Every time I try to upgrade to vista it goes through the install in its entirety, then when it is done and boots up vista for the first time, it says that the installation failed and it rolls back to my xp installation.

The Vista Upgrade Advisor says I'm good to go with only one conflict (it says my integrated networking controller (Nvidia ethernet controller) is not supported (it is), but will not interfere with the installation anyway.

My system is the following:
AMD X2 4200+
2 GB corsair xms pc 3200 DDR RAM
ASUS A8N5X mobo (socket 939) (NFORCE4)
EVGA geforce 7900gt
Corsair hx520W PSU (not that it matters...)

I have some peripherals also, but detatched them for vista install (and don't have the drivers installed either)
X-Fi platinum
Linksys wireless networking card
Rosewill PCI serial com port card

Please help! I have tried installing 4 times, no luck
Thanks alot in advance.

 

Make sure you update the BIOS, try the Vista upgrade again.

Steve