i disk clean up my hard Drive/disk Everyday neraly after every 1 hour so is there any bad effects of doing it and is it good to do it?

These pop up when not on Internet,then on Internet have pop ups from classmates.com. How can I get these to stop, I have uninstalled registry cleaner that the fix it is from but it still pops up.I can’t find them on hard drive or in WIndows.How can I get this to stop or get off computer?

What is the easiest way to wipe my hard drive,etc… and do a clean install of Windows XP ?

I’m having trouble doing the task, it says no hard drive found.

I want to make it so my computer is like the day I bought it. So basically wipe the hard drive clean and stuff like that. How do I go about doing that?