....and you have provided no courtesy. Not much of a stimulant, PJP.
You might, in any order you choose:
1. Borrow another CD & try again.
1a. Think about the results.
2. Try your CD on another machine.
2a. Think about the results.
3. Copy your CD to your HDD and try the install from there.
3a. Think about the results.
4. Based on results, decide whether to
(a) deal with Microsoft directly for a replacement CD, or
(b) search the web for an illicit copy of the file (or the CD), or
(c) get a new CD drive.
Above all, do what you can to think. DL's answer pretty well covered the
bases. This newsgroup doesn't do house calls, or generally react well to
the determinedly impolite or wilfully obtuse. Handholding happens, but
rarely in response to a followup post like yours. Nobody really knows
why for sure, it just seems like that's one of those mysteries of life.