I have a Dell 531S with 3Gb memory I bought about 2 years ago. A few weeks ago I started getting latency on basic desktop functionality. The system continued to degrade to the point where various subsystems would conflict with each other and nothing would be happening. I ran about 15 different virus/rootkit analysis and found nothing. I then overlaid the OS on the existing file set. The problem continued and I just reformatted the drive and do a fresh install on the same drive (C . I ran a memtest and it does not appear to have any issues with the memory sticks. Even after the fresh install I still get latency and the desktop hangs up...mainly when searching IO devices (external drives) and the internet. Any suggestions on what else I might look at?
That's odd that a fresh install wouldn't help. Have you tried just doing basic things like turning off the Aero functions or changing your power management settings to see if that would have any effect? It may not outright solve the problem, but it could contribute to helping it.