Hi,
I also have a very low-spec machine (until next week..hehehe),
as mentioned above Corn will play mario at a very decent rate.
But don't limit yourself,
1964 seems to be OVERALL faster than PJ64 (but still give PJ a go)
I find that I can get a lot of the games to run at a playable rate by,
1) Turning off sound , unless it's critical for the game (by that I mean choosing the "no sound" option , not just turning off the speakers

)
2) Right clicking on a rom and choosing rom settings and then raising the counter factor (most games are not affected up to a CF of 5)
3) Closing down any applications I have running, and any unnecessary background tasks in the task manager.
Resolution within the video plugin does not seem to make a jot of difference like it does in PC games (can anybody tell me why this is ?)
If you wanted to take it a step further and give a maybe very big increase then you could try over-clocking your chip (although I'd make sure you look around on the net first for this step).
Hope this helps you
Good luck
