Ive never really paid close attention to how much free space I have, because Ive always had plenty. I don't have any big programs, and Im am constantly doing maintenance. Deleting temp files etc. Now, all of a sudden Im down to 10% free space. Ive done disc clean up, but there isn't anything for me to clean. Only thing I can think of is maybe using system restore too many times. Or does that make a difference? Help!

This should gain a noticeble amount of space if you have not done it already
When you do disc clean up and you get the screen to choose which files you would like to delete, click on the More Options tab on top
Now click the Clean up tab under system restore, and say OK

This will delete all restore points except for the last one that was made, so you dtill do have the last system restore point

Have you also delete your browser files,
In IE, tools and click delete browsing history and choose which items you would like ot delete