Ok steps to reinstall:-
1 -restart pc - when BIOS screen come us press (F3 or F8 to access BIOS, it will say which on the screen)
2 -when in the BIOS there is a boot sequence menu... you want the 1st one to be CDROM (should have been HDD previous)
3 - set the 2nd 3rd 4th to disable SAVE and EXIT BIOS and then when the BIOS is booting up again it should say 'press any key to load from boot device'
that should then be it and then you need to choose the drive and go through the motions of loading the OS.
Have you checked in windows that the CDROM is working?? (if on a tower PC and you have more than one CDROM - remove the slave one via the cable and load from the master)