RAM or CPU?  

hey eob,

First of all before you do anything I would run a virus scan, and a spybot search and destroy scan, a couple free programs, Avast one of the better anti viruses out there, as well as Comodo (who I have not tried the antivirus software yet, but sing their praises on firewalls) and spybot search and destroy, I would run these scans first to see if your computer has any kind of virus adware/malware/spyware on it.

I would then consider upgrading the memory, and check with the computer to make sure the max it holds,

if you have a recovery disk and not a lot on the computer that you care about copy files pictures etc and do a system recovery with the CD, if you don't have the CD, you should be able to contact the mfg and get one.

I would try all else before doing a system recovery, but my first thought is to check for anything on your computer that you don't want there

Avast is one of the best out there and its free,

Also it could mean your hard drive is filling up, you might need to take some stuff off the HD< and defrag the hard drive.

Hope this helps you
Mooch