Doesn't Format C Drive Instead To Create Windows Old Folder

I brought windows 7 pc before 6 months. I did not know even abcd of computer at that time. I installed lots of software and games without having proper knowledge. Even i delete registry files thinking that, they are not useful to me. so i got serious problems on my pc. I finally format my pc a month before. As i describe earlier without having proper knowledge, just reading few post on internet i just insert my windows 7 cd, and install it like normal software without booting cd. It install smoothly without having any problems. The only thing was that, it doesn't format c drive instead it create windows.old folder. I delete it safely reading post from internet.Now the problem is for speed up my pc i decide to try xp on it. so i brought xp cd. I understand that without booting it is not installing xp on my pc. So i follow normal procedure of booting cd(Restarting pc and pressing f12). There was options like boot from hard drive, LS120, CDROM . I select cdrom. After that there was message "Verifying operating system Boot from cd/dvd. " for 2 second. After that it take me to the normal windows start up. I try these lots of time but i am unable to boot cd.I even try it with windows 7 cd but i am steel getting same message.Does this is because my first wrong formatting of pc.