Help-my hard drive is full of "NOTHING"!

I use a laptop with two drives, the smallest of which is 4.99Gb but it only really has XP (SP2) and Program Files on it because it keeps filling up with nothing (as far as I can see). It currently has 338mb free but 4.66GIG used). Virus checks are negative but I can't run Help anymore (it just doesn't appear if I click on it) and I can't update Ad-Aware because when I try it says that everything is up to date (despite using the update from October 1984!) This is very suspicious and I think that formatting the drive and reinstalling XP would solve it but it will be awkward if I lose all the Program Files! Any ideas guys? (PLEASE!)

 

Hmmm. is this the boot disc? if so windows xp and a "few" program files will fill that up( xp recommended instal(10-12 gb)) It is most likely filled with hidden or files the pc uses to run windows.

 

Thanks - yes, XP is on that disc so maybe that's the root of the problem. But it has never had the drive so full (and it was OK before!) and of course, that's my laptop but the desktop is quite happy. And now - 4.66Gb used on the laptop? Somwething strange is happening!