vista using 100 resources

I'm running Vista on a 3.2GHz P4 machine with 2GB RAM, Medion Radion X740XL graphics card.
Using Aero glass theme, on initial startup the Task Manager Performance tab shows 100% and the CPU fan quickly runs up to maximum speed.
The cure is to select Windows Classic theme and then re-select Aero glass theme. This brings the performance down to 0-1% for the rest of that session. Upon next startup, I have to go through the same procedure.
Any ideas?
-- Exiddor.

I'm running Vista on a 3.2GHz P4 machine with 2GB RAM, Medion Radion X740XL graphics card.
Using Aero glass theme, on initial startup the Task Manager Performance tab shows 100% and the CPU fan quickly runs up to maximum speed.
The cure is to select Windows Classic theme and then re-select Aero glass theme. This brings the performance down to 0-1% for the rest of that session. Upon next startup, I have to go through the same procedure.
Any ideas?
-- Exiddor.