Hi. This question is probably well known to all of you, but I've already searched all the pages and cannot find solution for my specific problem. The thing is, that my usb external disk hardly works. You know, sometimes I connect it and windows 7 detects it without any problem, but right now nothing happens. And I mean that blue light is on, I can feel vibration of rotating disk, but computer cannot see it. Things I've already tried:
-reboots (with or without disk connected)
-changing bios settings to default
-showing disconnected devices with command line in dev. manager and uninstalling drivers
-looking for it in drives manager (no sign of it)
-connecting to another pc (still the same)
-connecting to another usb port
-disabling automatic power off in usb root settings

All of these things sometimes helped, sometimes not, exactly as I would do nothing. And none of them is the one that always helps. For me, the same behavior on another pc prooves that it's disk's fault. What should I do? I never dropped it and always treated carefully. Could it be kind of virus? Or general mess? If so, what software should I use to repair it?

Thank you in advance

IT could be a number of issues. Diagnosis over USB is not accurate, extremely limited and ideally you should remove the internal hard disk and test it against a direct SATA connection. Download MHDD and see if it is identified. At this point you will be able to get a much better idea of your problem.