I use Process Explorer from Sysinternals (it's one of the best), to track this kind of issues or malware running etc..
I began to have this CPU picks after install of the Windows Genuine Advantage tool.
Anyway it is not quite a big issue because it doesn't happen everyday and with the same extent.
For example, I had today an update, I think, related with the last VML exploit.
About my disk it is two months old only, it is in fact the newer part of my PC. The oldest is the motherboard and processor (Athlon XP 1.3).
Thanks for your ideas about this. If something goes odd I will open a new post.