Hi have dual boot XP + upgrade Vista. Before i start can someone tell me if i reinstall will my upgrade key still work?

Ok here goes ...
i decided to use system restore after installation of a trial version of ulead videostudio 11 plus.
after system restore when vista loads, it shows a mouse pointer over a black screen with the hard drive active. Sometimes only black screen no mouse pointer. The startup screen loads (the one with the green bars on a black screen) but it does not load the logon screen. Same thing happens running in Safe mode. Have not tried holding that key that lets you choose which drivers to load (err have to search can't remember ... was it Ctrl?)

The thing is, this has happened 3 times before but when i restart it, Vista loads with no problems.

Any other alterations? Well i installed some drivers from manufacturer for my hauppauge pvr pci ii 26xx card but i am sure i have restarted that before and it worked.

Howabout restore further back? Well i shouldnt have loaded xp but i did and all my restore points have been erased. But i doubt it would have helped. Would it?

Diagnostics - the Vista CD repair diagnostics found no problems.

So ... what's the problem guys? Do i really have to reinstall and if i do will my (upgrade) key still work?

Thanks for Any information!

ps i will try loading one driver at a time soon ... my baby is crying, just thought i'd get this out into the open early so i have it up and going by monday!