Okay i used EVEREST to measure CPU Usage levels while running PES 2008. Anways this is how my pc shaped up before, during and after running PES 2008:
This is my CPU Usage about 5 mins after startup running nothing except background processes and the like:
This is my CPU when i started PES 2008 up until when i finished:
The red circles represent:
1 to 2: From when i started the game to when i began actual gameplay. (ie. in the menus)
2 to 3: Actual Gameplay up until when i minimised the game to check what was happening with cpu usage.
3 to 4: Actual Gameplay till when i got out of the game and returned to PES 2008 menus
After 4: From PES 2008 Menus to Windows Desktop
Now this is my pc about 30 seconds after i exited PES 2008:
As you can see my CPU only seems to be stressed during gameplay but after i exit PES 2008 it runs just like it was before i began the game.
BTW i run PES 2008 on Medium Settings while using Kitserver.
Also my OS is Windows Vista Ultimate 32-bit and my CPU is a measly 2.4GHz Pentium 4.
Now im not sure why your cpu would be doing that...im no expert on this stuff...but have you looked at your cpu levels before running PES 2008?? Maybe a backround program could be causing it??
Anyways i hope that helped you!! If you have any questions ask away!!