Need help diagnosing and fixing a PC slowdown.?

[James]

Ok. My PC was working perfectly in the morning Wednesday. When I started it up again Thursday, I discovered it taking forever to respond to mouse clicks, opening programs, etc. When the programs finally open (after 5-10 minutes), they run normally except for Firefox. When Firefox runs, I constantly see "Not Responding" messages and scripts won't run. It even takes forever to open the control panel box or for the options to appear when you go to logout/shutdown/restart the computer.

I started it up in Safe Mode and the problem is not present in safe mode. I ran scans with McAfee and Malware and found no problems. I even ran disk cleaning and defragmenting and the problem still exists. The computer is old and runs XP, but that doesn't explain how it can be working great one day and be a complete slug the next day. I know some windows updates were installed as I was shutting down the computer, and those were the only things to be downloaded in the past week and a half.

[Nethermane]

I recommend downloading the free version of CCleaner and running that to clear up some free space. Also McAfee is a MASSIVE pc hog, they are huge files that are difficult to remove from your computer. I recommend switching to the free version of avast.
Browsers can build up a lot of memory and CCleaner can help clear it out. E.g. my internet explorer had 1Gb of memory taken up that was cleared up.