COMPUTER STUTTER DRIVING ME NUTS

I know this looks long winded but I feel I need to explain the background to the problem as it may be relevant. I am not a computer expert and the solution to this problem may be obvious, but I haven?t got a clue. So please help!!!!!

System specs: Pentium 4 CPU 1.70GHZ 1700MHZ, Memory 256MB

For the last couple of months my computer has developed a stutter. By stutter I mean every two seconds everything (mouse, programs, internet connection speed, keyboard etc) ?freezes? for a split second then returns to normal, then freezes again two seconds later. This happens at completely random times and can last indefinitely or for a random amount of time before retuning to normal. When it lasts indefinitely and I am forced to turn the computer off, sometimes it disappears and other times it continues even before I have logged in to windows. It happens regardless of the level of cpu usage or amount of processes being run. It also disappears for days and weeks before returning.

At first I thought it was a virus or spyware. So I downloaded Zonealarm security suite, Lavasoft Ad-aware SE professional, Spybot search and destroy and Tuneup utilities 2004 in an attempt to find out what it could be.

The computer did have a lot of spyware, adware, Trojans etc which I removed using the above programs. Although after I removed all the spyware, adware, Trojans etc reported by the above programs I was still having many problems, I downloaded Pestpatrol in order to see if it could find anything the other programs may have missed. Pestpatrol did find some problems but in attempting to remove them the system crashed. After re-starting the computer I could no longer log into windows.

I then was forced to bring the computer to a specialist who tried to access the computer various ways. Although I recovered some word documents (for my thesis! Phew!), the rest of the hard drive was lost.He said it was most likely caused by a virus. A full system recovery was then carried out and the hard drive was returned to scratch (as if it had had just come out of the box brand new).

Although I had lost everything I saw this as an opportunity to start with a fresh system. I started using Mozilla firefox instead of IE explorer and re-installed Zonealarm security suite, Lavasoft Ad-aware SE professional, Spybot search and destroy, Pestpatrol and Tuneup utilities 2004. But after a while the problem returned. All the previous problems (trojans, spyware, adware, viruses) are no longer an issue and the computer is clean, but the stutter persists. There are no visible suspicious processes running at startup, in task manager or in my hijack this log. Could this mean this is a hardware problem? If so what could it be? Or could whatever it was that crashed my computer have survived somehow and just isnt being detected?


Your help would be very much appreciated.
Thanks in advance.