ATi to Nvidia Card swap problem

[tagbartok]

Today I busted the piggy bank and bought a BFG 8800GTS 512MB from OcUK. Great price and they're only just down the road.
Unfortunately I have hit a snag. I uninstalled the ATi 1900XT using Driver Cleaner Pro and fitted the 8800.
The system now hangs after I log onto my account and get as far as my desktop. It's so bad I can't even boot into safe mode.
I've refitted the 1900XT and all's fine again!
I've checked and rechecked everything. I suspect it's a driver or registry issue.
I spoke to OcUK support and he said I may have to do a full reinstall of Windows. I could really do without that if possible at this time.
I've never had this problem in the past when switching from one manufacturer to another.
Any ideas please?

 

[tagbartok]

Hi folks
I'm running the ATi 1900XT again after another failed attempt at getting the 8800 working.
I've used Driver Cleaner to the letter of the instructions again and it still hangs in Windows. I can't get any further in safe mode either.
I can't try the card in another machine as no one I know has anything similar.
If it was a major card fault then I don't think it would let me get as far as I am.
I think it's registry so a fresh install of Windows looks to be the only way.
In 14 years of building PCs and swapping hardware I've only had one similar experience and that was with a Black Widow SCSI (anyone remember SCSI) scanner which incidently came from Millenium Computers before they were merged with OcUK. That cost me a new motherboard!