How to reformat?

Re-formatting should be a last ditch defense against certain undesirable programs. To make sure you understand what it does, it clears your entire hard-drive then installs a new copy of your operating system (or you can just reformat, but then you're bricked). A few problems may arise from this... You'll have none of your documents (obviously) and none of you previously installed programs. But the worst thing possible would be the lack of drivers, which would mean you'd have to manually install them all...

But what Bacon said was correct, just insert your Installation CD, and reformat for NTFS.