Emulator slow down

[Guyver-1]

Sorry if this is in the wrong section, it's dealing with older emulators so I figured it'd be placed here. Anyways, recently I've gotten back into the Emu scene and well the emulators just seem to start randoming slowing down during gameplay. I use ZSNES 1.51, Nestopia, and Gens+. A couple months back they used to run fine, even when I was fast forwarding the games, but now I run into major FPS lossage. Nothing on my laptop has changed besides the emulators. I tried going back to the old versions and even wiping out all the files and getting new ones. Still the same problems exist. Any ideas what could be causing the slowdown? My specs are:
Intel Celeron 2.4 Ghz CPU
Intel 82845G/GL/GE/PE/GV Graphics Controller
640 MB of RAM

If you need another other information about my laptop let me know. I really want to enjoy the classics again so if anyone could help I'd really appreciate it.