Sorry for the slow reply - I was on holiday
A dual core 2.4 GHz should have no problems at all with Stereo Tool. The RAM is a bit slow, but especially for the Generic presets there should be no problem at all.
BUT, if the CPU load is 99% it seems to be overloaded regardless. What happens when you turn ALL the processing off? (eg. just press the RESET button and then play some music). Also, can you try what happens when you set the "screen refresh speed" slider all the way to the left?
You are playing MP3s, right? Are you using the normal MP3 decoder that's in Winamp by default, or have you downloaded another one?