I've been working with software installation issues for the past four years. I can tell you that you havent tried everything until you've F-DISK'ed it. Pain in the ass, I know, but it's an option if you've tried everything else. I've also had to resort to upgrading the BIOS on the motherboard, replacing hardware - starting with the cd/dvd rom first. And yes, sometimes even that does not work. There's certain computers where certain software just will not install, no matter what and you may never know why.
Worst offender - Toshiba laptops.