Little help with rom issues

Hi, I'm semi-new to this whole emulator thing and I've got a few problems with various roms. Now most roms run fine with little to no lag at all however I've got a few that play horribly. They are Mario Tennis, Super Smash Bros, and Crusin USA. The problem is that the sound is all choppy and sounds very unplesant. The video's fine I'm and my sound drivers are up to date so what's the problem? I use all the default plugins so is there an issue with those?

Any help would be great!

Oh right! Forgot that in my first post.

I'm running "in bwteen" the minimum and recomended sys reqs with this...

CPU: Intel P3 1 Ghz

Memory: 740 MB

Vid Card: 32 MB ATI Raedon 7200