This is a strange one, if I plug in my usb flashdrive into my windows 7/64 laptop and bootup, it finds it ok and I can read and write to it no pproblem. If however i remove it and then replace it whilst still on, it tells me that the disk needs to be formatted. If I do format it says - Can't format. If I take this flashdrive to any other PC including an identical spec windows 7/64 machine then it works with no issue. I've tried deleting drivers etc to no avail.