I have searched numerous posts on external hard drive issues here, but not found a solution to my particular problem. I have a WD Passport 100Gb, USB, external hard drive that was being used on a windows pc as a back-up drive. I have since, successfully formatted it for use as a back-up drive on the Mac via Disk Utility and have been using it with Time Machine without any problems. It has proved to be a little small as a backup and has been replaced by another larger ext drive which is working fine. I now want to re - reformat the smaller WD disk back to be recognised on my Windows machine so that I can use it like a large memory stick and move Windows files (not Mac files) back and forth to work from home. I don't need to use it on the Mac again. I have been singularly unsuccessful in getting the Windows machine to load the drive and recognise it. I feel sure that I have successfully converting the drive back to MS-DOS Fat32 format from Mac by using Disk Utility, but the Windows XP Home machine just refuses to recognise the drive even after repeated attempts to set it up as a Fat32 drive with one partition, set with a Master Boot Record 'scheme'. When I plug it into the Windows machine, it ticks like a clock and is recognised in Device Manager as a drive, (but not Explorer) and appears with an Error triangle, and in the 'properties' of that the drive is noted as "cannot start". The Mac manages to see it and write files to it, so something is amiss - any ideas please? It sounds to me like a driver problem, but there don't appear to be any drivers for it on the WD site. I am using a relatively new iMac with Leopard and a Windows XP machine separately.