I have been experiencing a recurring slowdown on my PC for about a year. Basically it would run fine for a while but then would just start dragging & was only usable for limited browsing. No photo editing was possible. It always seemed to happen following high memory or disk usage. I did all the virus scanning & spyware checking possible, ran process explorer & file monitor to look for something eating up cpu. Nothing found... reinstalled xp home... took the stupid thing to CompuRussia and even had them look at it. Then I bought & installed xp professional and it seemed to go away for a while. But it was just a dream now I see... it was all just temperature & timing. You see... summer was at an end when I bought XP professional.
Note: I had never taken a PC in for repair until that time. I cut my teeth in computers maintaining PCs, but I figured maybe it was just something new. They didn't figure out anything except how to charge me for excess labor. Turns out it was a new problem to me...
At lunch today I was explaining the issue to a couple of coworkers for the 10th time and Ben said it had to be either a driver or hardware related. (nice narrowing of the field, ha) I decided to assume he was right & started looking at the hardware. When I got home today, the PC was slow. I went to "My Computer" & clicked "View system information" to head to the device manager to review what was installed & see if anything was showing a conflict or trouble. Before I clicked off the main tab, I noticed that the reported CPU speed was only 836 Mhz!!! No wonder it was running slower. The CPU had been stepped down from its regular 1.67 Ghz speed.
Wonder what would cause a CPU to slow down like that? All I could come up with was temperature. I did some googling for "cpu temperature slowdown" and came up with this article. My cpu seems to fit that Athlon XP 1.33Ghz+ category & max out at 90°C. Recommendations are for 20°C less than the max temp, or 70°C.
To test my theory I rebooted my PC & verified it was at 1.67Ghz. I downloaded speedfan and measured the temp. Temp 2 was at 68°C, which was close enough to 70°C to keep me looking. I started up Norton (a past trigger of the problem) and also started opening images in Nikon Editor to suck up memory. To make things worse I started modifying the images rather randomly which always causes Nikon Editor problems... seems to keep a big ass undo buffer or something. As soon as it spiked to 70°C, the system began to crawl. It took a while, but I got the system properties open again & I was back at 836 Mhz.
I've since taken the cover off my PC & will probably add another fan somewhere eventually.
I hope this problem stays solved.