What operating system are you trying to install, first of all?
Usually, unless your trying to install an operating system before Windows 2000, you'll be able to insert the CD and just let it run through.
Check your BIOS settings and ensure that the CD-Rom Device is set to be booted up, before the hard disk.
EDIT: I see that you've posted a thread yesterday regarding this topic. Unfortunately, it is not legal to use an illegal copy of Windows XP, and therefore we can't help you do so on these forums. I wish you the best of luck in fixing your issue, but advise you to follow the law when using your computer.
Link to original post - http://computerforums.org/showthread.php?t=47975
Please also remember not to double post in other forums, as thats also frowned upon.