I have 2 usb drives connected to my pc.Both has 80 Gb spaces.One drive was working okay but one until recently went a little crazy.Sometimes it is recognised by XP sometimes does not.Now I have the feeling that the power supply ( a small adapter ) is not supplying enough current to the drive - to power the small circuit board and drive and the same time....I've tried connecting it to a normal psu current and it work well.....do this occurs sometimes ??