BleepingComputer.com: My girlfriend has a broken registry

Hi, this is my forst post at this forum, so I'll try to keep it fairly simple.

My girlfriend has a old laptop she got from a friend. It's running Vista, and it was doing alright until she accidentally downloaded a rootkit or a worm (we're not exactly sure). Whatever was downloaded locked her out of her computer on her next restart. When she tried to start up her computer, it would boot normally, but before it finished booting, a black screen with some words saying something about a registry error (it only flashed on screen for half a second or so) appeared, and then restarted her computer. This cycle continues indefinitely until one manually shuts off the power by holding down the power button.

Now, I have one of those "pop your laptop hard drive in this case and it becomes an external hard drive" things. I've been able to go into her hard drive by plugging it into another computer, just in case we need to pull the information off and wipe her hard drive. Is there any possibly way to remotely fix her hard drive? And if not, what would be the fastest/most economical way to wipe and restore her hard drive? (By the way, we do not have anything to install it with, given it was an old friends.) Thank you!

The fastest thing would be to use the external case to hook to another computer and save her data.
Presuming that there's a valid Windows product key sticker on the laptop, contact the manufacturer and ask for a set of restore disks. They're cheaper and more complete than a retail copy of Windows Vista (they contain the specific drivers whereas the retail Vista may not have them).

Once you get them, follow the instructions to boot from them and follow the instructions to wipe everything out and reinstall to the factory specifications.

Yes, it's Genuine. Okay, so, I'll transfer her data onto a safe computer, thank you Is there any way to completely wipe and install a copy of Windows Vista onto her computer without buying anything? I don't mind using torrents...

It's too late to do it now as HP tattoos their disks with the mobo make and model.
The cheapest solution is a set of recovery disks from HP. Last I checked they were under $20 US and you could get them in 4 or 5 days.

Okay, thanks!