new mobo / mysterious CPU usage

i recently changed my board to an asrocks kt800+.

Everything works quite good and fast, until I start multi-tasking.

Once I usually start running winamp, yahoo messanger, aim, and a variety of programs, my music start pausing. My mouse bairly moving.

I check the task manager and I notice the CPU usage spiking. Sometimes its at 100% sometimes less.

Even after I close all the programs down, my computer lags for the rest of the session. The CPU keeps spiking up and down.

The wierd part is that in "processes", the CPU does not add up to the "CPU Usage" at the bottom of the screen.

What I've done so far,
1)disabled ethernet
2)disabled 2nd harddrive
3)changed slot the ram is in
4)reduce virtual memory
5)played with bios
6)played with services
7)updated video drivers
all system hardware is functioning
9)CPU temp at 38C
10) Disabled system recovery (this has actually helped a little)


Note: I did not re-install windows after changing the mobo.

Is that what I need to do next? Its just bugging me I can't identify where the cpu process is going.

thanks for the help
dan