I have been told this helps with computer performance but have no idea what I am doing, can anyone put this in really simple terms for a computer idiot like me? Thanks
In which case, your hard drive's primary partition (almost certainly what you know as the C:\ drive) will be formatted using NTFS rather than FAT. Fragmentation is built into the way NTFS works, so defragging will make (next to) no difference whatsoever. As soon as the process ends and you start using the computer again, it will fragment again...