I have a virus on my pc, Iwant to erase everything and start from scratch, however i dont want to be unistalling the OS and reinstalling it cause it takes to long, is there a way I can erase everything but still keep my OS on my pc?

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?

Computer is generally too slow!

i want to free up some disk space on my windows 2000 xp system
first i go to start, then to programs,
then to accessories, then to system tools,
then i go to clean disk, once i get there and click it gives me several blocks to check in green or un check i usually check all of them.
it removes all of them but is not removing the stuff contained in the "compress old files" block. what’s wrong? how can i get this to work?