XP application is chopped as Parallels competes with OS/X

Mac Snow Leopard and //=5.0

I have an application which is getting switched in and out as OS/X does some background tasking. This started in the last few weeks and I'm not too sure why though I did have to do a re-install of 5.0 ..... thus, I may have mal-configured Parallels.

The issue is rendering the Windows XP program useless as it creates tones which get output to something else ... if the tones are contually, brutally chipped up, well, the output becvoomes meaningless.

Any ideas on how I can optimize parallels to occupy more of the Mac CPU(s)

MacBook-Pro