Slow fps in mupen64plus

Not sure if this is the proper place to post, if not, please recommend the proper forum.

I recently installed Mupen64plus v1.5 on a Kubuntu 9.0.4 linux box I'm building for my nephew. Zsnes emulator works great but i cant seem to get the mupen64plus to play at a proper fps rate? Whenever i launch either super mario 64 or legends of zelda ocarina i'm getting fps rates hovering around 2.5 fps. It loads supremely slow. I've tried both the Glide and the RiceVideo plugins but get similar results. I saw on another forum it could be related to the audio limiting the fps rate, but when i look at audio settings i dont see a box for unlimiting fps rates? I've tried a little messing around with both video and audio config with mupen64plus but honestly i dont really know what im doing. I'm worried i might be trying in vain to use an emulator that is a little too much for my antiquated machine. Can anybody steer me in the right direction, as to whether or not my computer is not enough machine for mupen64plus or what optimal video/audio settings might be for a slower machine. I'm obviously both a linux and emulation newb, but nevertheless I do think this would make an awesome learning tool/toy for my nephew so I'd like to at least try.

My system specs are as follows:
AMD Athlon XP 2800+
NV28 [GeForce4 Ti 4200 AGP 8x]
cant find memory specs but I think its 1GB memory

Thanks

Funto, i owe you a beer

After a lot of tinkering I finally figured out how to install the proprietary driver for the nvidia video card and now the fps is working like a champ! Looks like it should, so much thanks to you.

Do you happen to know much about the audio plugins for mupen64plus by chance? The reason I ask is, now when I try to close the window for emulated game (Super Mario 64 in this case), I get a looping error that locks up my machine, and the error says:
"the core thread received a SIGSEGV signal. This means it tried to access protected memory. Maybe you have set a wrong ucode for one of the plugins!"

I tried looking up on the web what could possibly cause this and from what I could tell other people were saying it was either the video or audio plugins. So I tested by turning off both, one at a time, and I found when I turn the audio plugin to No Audio, it doesnt crash. So I'm guessing it is the audio plugin, but I only have one audio plugin option and that is JttL's SDL Audio 1.5 with the following configuration-

Config:
Volume Control: Internal SDL
Change Volume by: 5
Sampling: SINC
Default volume: 80
Swap L/R channels - unchecked
Default frequency: 33600
Primary Buffer: 65536
Secondary Buffer: 2048
Buffer low level: 16384
Buffer high level: 32768

Is there another audio plugin out there I should use? Or should I change the config settings on these? I checked and it doesnt look like there are any proprietary audio drivers i need to install, but possibly i'm looking improperly. Any ideas?

If not, totally cool, I'm just glad I can see it. Audio would be great, but I'm still a happy camper without it. Thanks again for your help.