Sound with Windos XP

I am having problems with sound on Windows XP. I am running a AMD 1.2 with 256 mg Ram and have a soundblaster PCI 128 sound card. Everything says that it is installed correctly. The sound plays fine as long as there is more than 30% processor in use. The windows sounds come out as a bunch of bad noise.

Does anyone have an idea or incountered this problem.