windows 2000 perfomance problem

Hi ,
I’m using windows 2000 pro. Since last week, I realise that my computers performance was getting slowly. When I display task manager, I always see “CPU usage %100”. “Memory usage” is in high level.
When I want to print a page, it takes several minutes. ANd other applications like outlook, office are running very slowly.
There is no virus attach. I just scaned new updated Norton Anti virus.
I ran maxmem tool for optimizing memory. But I couldn’t solve this problem.

I’m not sure, is this a memory problem or not?
Could you plase, tell me any suggestion to solve Thank you.