i'm not sure i understand.
reboot your computer with the disc in the drive, when it says "press any to boot from CD", press a key. if it doesn't say that, then you need to set your bios options so that it boots to cd first.
after it boots to the cd, you will have the option of wiping your drive clean and reinstalling windows. you will lose all of your data, but i assume thats what you want to do.
i hope i answered your question.
MY 1337 SYST3M:
(1)case - generic
45jiga-hurts intel pentium VIIteen hollywood
some more ram.
asusapaloozatron v7542 mobo