Last night I was trying Lost Planet at fairly low settings when my computer froze. So I reset it, but when it started back up a message saying that a config file was missing or currupt and that I had to repair my XP installation. I rebooted a few more times just to find the same message. So I went to do a repair, and got to the input admin password, which I did, but it said that it was invalid. I tried this at least 10 times to no avail. So I reverted to a reinstall of XP which got me back up and running. Everything in my system seems to be very stable. This was on the system in my sig.
To do a repair install you proceed as doing a new installation.
It will tell you it found a previouis Windows installation and offer to repair it.
The process looks just like a new installation, except when it is finished all your files and most of your settings will still be there.
I don't think you need the administrator password to do a repair. You do need the serial number of your OS.
It would not let me do a repair without a password. The only password I ever set it would not accept, so I had to do a reinstall. Luckily all of my data was on another drive so I didnt loose anything. It just seems strange that it wouldnt accept my password.