Computer Usage Running High

Today I get on my comptuer and it is taking longer then normal to open up applications. So I do the three finger salute and looked at my computer usage it told me it was running at 100%.

I was wondering how could it be running at 100%, I’m only running firefox, msn messenger, musicmatch jukebox.

I have a Intel Celeron M processor running at 1.4GHz with 480 MB of RAM. It usually never runs this slow. Could it be because of firefox and the internet threat they had last week?

Any possible solutions are helpful. Thanks a bunch.

~mike~