Thanks for the repiles.
I've tried all of that but to no avail. Cannot start superfetch as windows cannot find it. Only joy I have is if I delete the prefetch folder, which works until I reboot.
I have not installed any new hardware, the memory stick is 4Gb and it has previously worked for readyboost on this machine.
Is it possible to do a windows reinstall whilst saving all thats on the HD? I've tried using the install disk for restore but it says no restore points available.
Cheers.