Try running a disk cleanup and a disk defragment.
Edit: And try uninstalling/deleting any programs and/or files you don't need or use very often.

Agreed, try removing all the crap (no offense) from your system. Free up your HD, then reinstall your emualtors after if they're still slow. I bet you got alot of HD space, right? lol.

If all else fails, try some C4, j/ks

Don't forget it might also be a virus/spyware hybrid that is taking away stuff. but yeah it is probably just you running low on space. try to get about 15% empty.

-Shoe

Spin around 4 times, lift up your leg, and lightly tap the monitor with an icepick while saying " I need to delete unused files". And that should do the trick. Yep.

I agree with what has been said so far, Virtual memory uses HDD space as temp ram when all of the actual ram is being used, it's much more slower and if you havn't defraged the HDD in a while this can slow things down, also if you have less HDD space you would get problems as there wont be enough for what needs to be used for the Virtual Ram, try also disabling some programs when playing games such as virus checkers and firewalls etc they are not needed when playing games (unless your on-line) and they can use up resources that can be put to better use.

You could also try getting more RAM for your PC this will lessen the need for virtual ram to be used as much if not at all, i dont know how much you have at the moment, but i have 1024 meg at the moment and the virtual ram doesn't get used much at all, only if I have a few programs running at once, hope this helps.