A couple of weeks ago I noticed my Win XP SP3 desktop PC (Gateway E-6610D) behaving in a peculiar way. After it runs for some hours Icons on the desktop start losing their names. Installed programs start giving errors. The start menu also shows some icons without names or they keep alternating as I move the mouse cursor. Normal command dialogues' windows like 'shutdown' or 'save' also show on the desktop without any writings which makes it very frustrating until I escape and refresh the desktop. The problem is only solved once I reboot only to recur again after some time. The re-booting process also hangs after some processes are stopped so I'm forced to cold-boot.
I have tried to scan the system with AVG and also Avira both in normal and safe modes but I'm not getting any infections and the PC still behaves the same.
Kindly guide me on how I can clean the system at least without formatting.