dll - Dynamic Link Library. (definately do not delete unless you know what you are doing) 1. If you use AOL, a good way to free up some disk space is to go delete all PREVIOUS aol folders. ie. Delete aol7.0 & aol8.0 if you are currently using 9.0 If you dont have any old installations then try cleaning out your current downloads folder. 2. Additionally run a search by clicking the start button and clicking search. Find all Files and Folders.... Once there do a search for *.tmp this will look for ALL temporary files on your PC. Once you have found them all highlight and delete them. (I suggest closing all open programs 1st) 3. If you use internet exlorer goto Control panel, click "Internet Options" and Click "Delete Files". 4. Other than that, try deleting mp3s you dont listen to anymore, delete movies you dont watch, pictures you dont look at. Also try uninstalling large programs you may not use.