External harddrive USB – only recognised in device manager

I have an external USB harddrive, that plays up intermittently. It is recognised in device manager, but not disk management or my computer. It has worked before, i lent it to a friend, it worked fine for her, she deleted EVERYTHING off it, and returned it to me, and now it isn’t recognised anywhere but device manager, which makes it pretty useless. i’ve tried uninstalling, reinstalling, removing it from device manager in both places, it still won’t be recognised. im using Windows XP.