I've encountered an odd problem... I had a computer with my sister's copy of windows xp on it, which worked great for the 30 days of trial (lost the registration key). After a month, I attempted to install a different copy of xp on it (didn't do any formatting or anything). Booting from disk, I was able to do the preliminary stages of windows install, and then it needed to restart... so I restarted, it posts, goes through bios, and after a screen which said "Windows install is restarting" (or something to that effect), it instantly shuts off.
I found that if I didn't insert the install disk, it would boot up and get to the windows install menu (the one that takes 39 minutes, or whatever), and sit there prompting me to insert the install disk. As soon as I inserted the disk (ANY disk, actually... install, audio, data) it would spin for half a second and then instantly shut off.
I suspected either a faulty disc drive, or maybe a dual-OS-booting problem.... so I tried a different cd drive with a different hard drive (HD had data on it but no OS), and same problem.....
...Thoughts?