Well, it could be a few issues.

1. Overheating. Make sure all fans internal are running well right from start up and that they remain running. Make sure no dust is plugging the CPU or CPU cooling fan or other needed air ways in the case.

2. Power supply. If it is going bad, there is no end to the eratic behavior it can cause. It can cause bad installs, hard drive not to function correctly, other errors and <cough> laggy computers. As well, last month my neighbor was going to have me replace his hard drive, he said it was bad. I opened up the tower and no kidding, the CPU fan looked like a gerble and the power supply a bird's nest of cat hair and dust. I cleaned it out, his clunky hard drive, laggy pc and other problems are gone.

3. Hard drive. It may be a bad hard drive. There are tools from Maxtor and other softwares that will check this for you. You can also try to keep a close ear on it. If you hear excessive clunking, arc welding\electrical sound, or some others, it may be a good sign the drive is ready for the binary yard. Keep in mind, an overheating\plugged up power supply\CPU will and can cause slow downs and noisy drive as well, cd\dvd drives not to function and read data correctly at a constant rate which would explain the bad install.

4. Could be bad data on the install disk, a scratch or two or three and so on...

5. Could be a dirty laser lens on the drive reader or your DVD\CD drive is going bad. Sometimes, well quite often, I have seen people have to unhook on drive(if Multiple)to get the install working right or they get driver conflicts when installing XP. A long shot but thought i'd throw it in anyway. Either way, it won't read data right.