I seem to have come across a major problem that has me entertaining the idea of formatting my hard drive and reinstalling Windows XP Pro.

Just a few days ago while in mid use my PC started to slow, applications running slow forcing me to try and close them via the task manager (ctrl-alt-delete).

Since then I have rebooted the machine numerous times (which brings its own problems, background processes not terminatinating - resulting in promts to End task) and run AVG virus software to detect any viruses as well as Ad Aware to root out any spyware that may be causing the slow down. None of them have resulted in any improved performace.

When the machine fires up, it reaches the log on screen as per usual with no delay, but entering any one of three user log ons results in the same problem.

IE, for that matter any application takes an age to open up. Switching between applications takes nearly as long.

I've done a brief search on the net to see if such a problem has been reported before but I can't find anything similar to this. I haven't downloaded any new programs which may have caused the slow down and cannot find any way to diagnose the problem.

Anyone come across anything similar or have any suggestions on how I can isolate the problem?