Vista - PC blocks when starting vista

Hi ,
I just installed a new video card MSI NX8800GT on a new Packard Bell that came with Vista pre-installed. I checked power supply which was sufficient ( 400w ).
Everything went smoothly also when installing the drivers which came on an MSI CD.
When restarting the PC he blocked when he was on the desktop screen.
After that it has been impossible to restart the pc. He blocks even before he starts uploading vista.
I am not a techy so I am desperate for a solution.
How can you get the beast up and running again if you cant even go past the begin screens ?
By the way, I did not make a recovery DVD yet ( foolish me)
Can someone help me ?
Thanks in advance,
Dirk

1st, Packard Bell?? talk about a bad acid flash back to 1996! Didn't even know they were still in Business. Didn't they get purchased by Acer or something like that??

2nd, what do you mean by "blocked" you said, "When restarting the PC he blocked when he was on the desktop screen." please define blocked?

No second PB. Never had trouble with the first one. This however is one with Vista.
With blocked I mean, no reaction any more. No pointer movements, no keyboard reaction...nothing. Just a still screen.
I guess I will have to throw away the HD ?

Have you tried Booting to the Vista DVD and running a repair on the install?

That didn't work.
The system was completely unstable.
Finally after allmost 100 times restarting the pc suddenly I was able to enter bios set-up and was able to destin the DVD as prime boot just before it blocked again.
Via the recovery dvd I am up and running again, but lost all data.
Never again Packard Bell, never again vista.
Did you know that the PC is quad core with a nvidea 8500gt and comes with a power supply of only 250w ????
Troubles guaranteed...
Kind regards,
Dirk
thanks m8 for your help

OK, if you are having issues ***While in BIOS*** this is not Vista - you have hardware issues. better check your video card - remove it and see if it stops "blocking" as you call it.

I guess you are right.
Upon installing the drivers of the new video card the PC became completely unstable.
But I now installed the Geforce 8800gt in my old Dell 5000 dimension that runs on XP ( I also changed the power supply to 400w )and this baby is running smoothly.
So I still feel that Vista is incompatible with some hardware drivers.
Or am I talking nonsense ?

Again, if you're having stability issues while your computer is in the BIOS configuration pages, then it is ***NOT*** Vista, but your computer - or, to put it more succinctly, some component(s) in your computer.