You need to find which F key gets you into the BIOS. It could be F2 or F10 or F12 or the Delete key. If these don't work then try them ALL (one after the other as fast as you can). Then you need to change the boot order to 1st boot from the CD drive.
If your really stuck you can do a "Windows repair/install". It will reinstall all Windows files and leave your applications alone. Go to this site for instructions http://www.michaelstevenstech.com/XPrepairinstall.htm