Why is it hungry?

[friedemann]

I am now getting paranoid in checking C drive properties to see hard drive space. It doesn't seem to improve very quick(if at all)
I started getting more careful when it got closer to 1.7Gb. No new additional programs, removed some. Minimal updates (allowing antivirus to get what it needs however>AntiVir<) Windows auto-update shut off, history=0 days, cache memory=0, pictures or music on C drive=0, bare basics to surf web. Initially had 2 gb hd space now .6.
Ran ad-aware, spybot,AVG8, EasyCleaner(toniarts),CrapCleaner,RegistryFirstAid >programs stored on a seperate drive installed and uninstalled after use<along with using Windows basic computer fixing functions.
Changed from FAT to NTFS.
No discernable bugs and yet am losing more hard drive space daily(power down computer every night).
Where does the memory space I had obtained go to? I mean, when I make free space on my floppies, they remain the same size until I ask to save something.
So what is asking what to store what? Why?
Really want to know because by that methodology, it doesn't matter how big the drive is, it will get filled up mystery crap - I would like to know how to eliminate the crap.(if it can go)
OS is Win XP Hd size is 6Gb, error free.
I am not reformating and I do not have access to the "restore" function of Windows easily.(its gone from the start button listing)
Someone have some insights to the Windows thievery?
Getting a larger hard drive is not the answer if MS is just messing with it. It is money out of my back pocket for no good reason.