Besides the pagefile setting, you may also check the temp file folders, windows dskcleaner sometimes won't do its work cleanly. Another thing to be noted is your My document folder. If you use the default setting, then it is in your C: drive and could eat up your disk space when you put things into this folder or when your have some games using that folder. and your mailbox file such as .pst for outlook will also expand over time and all the default location of these things are in C:, so there's a lot to do if you want to figure out the spaceuser.
