processor peaking

[np]

i have windows xp pro, my system seems to run smooth
except for my processor peaking at certain times.i run
all the smae programs ive always run and dont do too much
diferently.it seems now when i run basic programs(windows
movie maker,winamp,win media player)my processor starts
to peak and stalls everything.ive switched processors
from a amd athlon xp2200 to a xp2000.the problem still
exists.im assuming maybe motherboard but not sure. any
ideas that can help will be greatly appreciated.