XP freeze & CPU usage probelm

[tape]

XPpro SP3, 3GHz 3GB ram
Seems that my PC is always freezing up with 100% CPU usage. I can have a number of pages open in IE or be running iTunes or even Office. By the time taskmaster shows, the CPU peak has passed and things are normal so I can't see what is hogging the processor.
I do a regular sweep for malware (as well as active security), cleaning temp files, repairing registry and regular backup to 2nd HD. I do a clean install of system every few months and add programs as I need them. I have all my document files in separate partition.
Anyone have an idea as to what is going on or know of an app that would give me some info into what process is using so much memory?

[shadowpr]

I would just leave task manager open for a while, and then go about your business. Task manager is set to be on top (at least in vista it is), but if not, then you can easily switch to it when you notice the problem. Just click on the processor tab, and sort it by cpu usage.

Then you should be able to see he problem.

Also know that opening programs will cause spikes. That is normal.