There's usually only one good way to create more room on a computer. The tip on disk clean up is a great temporary task, but that extra space will fill up with the same stuff that was in there beforehand (the files windows automatically downloads to your computer every time you visit a web site etc...).
To create room, you have to delete some of the stuff you've downloaded. You typed that you download alot of large games, after installing them, delete the file that was downloaded. Might want to put it to disk before hand to have it later. Those games do not need the files that were downloaded that installed the games. If push comes to shove, could always reformat your Hard Drive. Would lose all of your information and games, so would have to back them up, then only put the files back on that you want. It's kinda a large and long process (mostly after wards, getting all the info back on) but will not only fix the -out-of-room- problem, but any other problems you might have. If you've never installed an OS before, I wouldn't recommend it with out knowing how. Might be with out a computer for several days.