Thanks, Saintly. Your tips are greatly appreciated.
Last night, I tried booting up and hitting F8 and even F5 (which I think is step-by-step confirmation), but the system seemed to ignore that and just boot straight into Windows.
I'm getting myself a 120gb HDD today and I'll partition it so that I've got a 5gb OS drive and the rest for my stuff. That way, in future, I can happily format C: without losing much.