I had an issue like this and it was because my CDROM drive was overheating. I had to remove the side panel to the case and get a huge room fan to blow into the case. If you have a CD Burner, try installing from the burner, they tend to have the best chances of reading scratched up CDs. Also, make sure your HD is good. If you have bad sectors it could screw things up. You might want to do a full format if you have not already.