Edit: turns out that clicking 'clean disc' cleared up about 20 GB, most of which is vista restore files. Somehow I'm not surprised... everyone always said Vista eats up memory...
------

This is a problem that may not actually be a problem... just something I'm CONFUSED about.

My laptop is divided into 4 drives. The largest of these, C drive, is 53.7 GB. It features the main operating system etc, as well as the user accounts. Currently there is 3.45 GB left, so naturally I want to clear up some SPACE, plus the thing as a whole is getting a bit cluttered. I decided the best thing to do was to see where most of the memory was being used, so checked on FOLDER sizes, getting something like that below;
Windows: 15 GB
Users: 5.23 GB
Program Files: 15.3 GB
All other folders: 195.83 KB (so 0.19 something GB I think. This figure includes the 'hidden' folders as well (like Program Data), or at least as far as I can tell)

Now, I like to think I can add up well, and to me it looks like I am missing about 20 GB of memory somewhere in the C drive. I've had the laptop for about a year now, and have noticed it slowly filling up (though am fairly sure I never had 20 GB free). I use McAfee security software, and as far as I can tell it is all up to date (virus scans etc never find anything) but to me it looks suspicous.

Does anyone have any ideas? I WOULD appreciate any guidance as to where to free up memory space, and if any extra INFO is needed would be happy to provide it, providing I can be told where to look for it.

Thanks in advance,

Avaris