Set the frameskip as high as it'll go, turning off sound might help but probably not, go options->emulator->speedup toggle (Note: You'll have to turn this back on every time you open the emulator, since VBA doesn't remember this setting).
Boycott advance is usually faster than VBA, but it seems to have trouble running pokemon emerald (it doesn't have any save settings that can be adjusted). Also, it's no longer being worked on, so if you have a problem with it, you're screwed.
No$GBA is also faster (and has some settings to make it even faster), but again, it may have trouble running pokemon emerald.
Bottomline: You're always going to have trouble running GBA emus on such a slow computer (I've got 500Mhz, and many games only run at 80~90% speed), but using a different emu will speed things up. VBA is perhaps the slowest of the GBA emus. VBA's big advantage however, is features and abilities. If anything other than speed is your main concern, use VBA. If speed is more important, use some other emulator. (Especially avoid any of the unofficial builds of VBA, they add features, but slow the emu down even more.)
Boycott advance is usually faster than VBA, but it seems to have trouble running pokemon emerald (it doesn't have any save settings that can be adjusted). Also, it's no longer being worked on, so if you have a problem with it, you're screwed.
No$GBA is also faster (and has some settings to make it even faster), but again, it may have trouble running pokemon emerald.
Bottomline: You're always going to have trouble running GBA emus on such a slow computer (I've got 500Mhz, and many games only run at 80~90% speed), but using a different emu will speed things up. VBA is perhaps the slowest of the GBA emus. VBA's big advantage however, is features and abilities. If anything other than speed is your main concern, use VBA. If speed is more important, use some other emulator. (Especially avoid any of the unofficial builds of VBA, they add features, but slow the emu down even more.)
