If your disc is legitimate, the errors might be caused by a scratch or imperfection in the disc. You can try cleaning the disc, but if that doesn't work, you will likely need to find a new cd. It is a possibility (though very remote) that your cd/dvd drive is failing, but a scratch is much more likely.
I don't think so, 'cause after I tried several times in Ultimate(64) I installed it with no problem in Home Premium(64). I don't think it's the CD/DVD neither 'cause I just used them (2) to install the OS and a bunch of programs.