A derp solution would be making sure that the harddrive isn't full. If you want to see what is taking up so much space on your computer, WinDirStat (
http://windirstat.info/download.html) is super easy to use. Just run it, let it sit, and when it's done, you browse files just like on Windows Explorer, and you right-click stuff if you want to delete it, etc.
If that is not the case, which it most likely is not, try defragging the computer. Defraggler (
http://www.piriform.com/defraggler) may take a while, but it can help make the computer run a LOT faster. Keep in mind, defraggler
will not create more space on the computer.
I hope that helps.