Well I ran the RAM test and it was fine, equally no resource sharing conflicts. Also updated all the very, very latest drivers as I was missing a couple, and updated the BIOS, but it was still doing it. I had win98 on before XP, and everything was fine. However, just today I've done a clean install of XP. Before, I was using NTFS as the file system for XP as apposed to FAT32, I've now changed to FAT32 and (fingers crossed) there are no problems as yet... if the horrible problem returns I'll be back here even more puzzled than before But thanks for the help anyway people