Between Windows 8 and probably not having a dedicated graphics card you're likely to find the real issue.
For the rest of you: Guys, disk space does not cause huge FPS drops unless 1: They don't have enough RAM, so they have to use page file, and 2: There's no decent spot to put the page file, because they don't have enough hard drive space, preferably consecutive, at all. Toribash does not need that much RAM, so this should never be an issue.
Pretty sure the Celeron is rather low end and primarily a laptop CPU, so if you're on a laptop, check to make sure that you don't have some dedicated GPU to go with it. If you do not have a dedicated GPU, and you are running a laptop, you are probably out of luck. Otherwise, you're on a desktop and you may wish to consider just upgrading the desktop or building a new one.