Bought one of these from Amazon and worked fine initially,was able to backup stuff to it OK. Tried it today and shows as drive G on desktop PC but when I try to access it it says 'insert disk in drive G'. Same thing on laptop (drive E) I had deleted some SanDisk software that was on the drive when I got it to make more room but sure it has been working since then. Does not need drivers for Win XP. SanDisk tech support say it is faulty but any ideas before I return it?