My brother built a new computer based around a new processor and motherboard, (intel Quad-core Q6600 and Asus P5E), along with a new case so it would be compatible(Antec 900). After transferring over these new parts along with the necessary older parts the computer works fine except for one problem. Everything powers on, the computer gets past BIOS and then goes to boot windows but instead he gets:

"Windows Error Recovery"
Windows failed to start. A recent hardware or software change might be the cause.

If windows files have been damaged or configured incorrectly start up repair can help diagnose and fix the problem. if power was interrupted during startup choose start windows normally.

Launch startup repair(reccomended)
Start windows normally

Whenever he starts windows normally he gets the blue screen of death and an instant restart. If he launches repair it goes to a loading bar that completes in about 5 seconds then just sits at 100% and does nothing.
P.S.
We do not have a copy of windows vista, it came installed on the computer and we never recieved an actual copy.
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To Tina G
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He cannot get to the actual desktop to do any of that from, windows will not launch.

I have a friend whos dell is full of viruses I rolled back the system to the earliest date and it still wont help ,I was told if you erace the hard drive and re install it would be better than if you just re run the program .Any advice ?

is formatting what the techs call f-discing.cuase if it is i can save money when i have it refurbished again or maybe you can tell me how to look for bad files that my anti-virus didnt catch and regcure didnt clean.

my registry is corupted and needs cleaned, how do I do it myself?