Sounds like your USB drivers aren't working properly. Or became corrupted or something like that. Did you do a complete reinstall of the windows operating sytem. Or do you mean you just reinstalled the USB drivers. Simply taking a Hard disk out and replugging it won't fix the problem.
Check your USB drivers in hardware manager section of control panel. Reinstall drivers from windows disc or other discs if there is a conflict or problem.
If that just won't work after a good go at it. Maybe you need a fresh reinstall from windows due to a corrupted operating system. Or a virus (if virus there are other ways of getting rid of without resort to fresh install )Including all drivers from other discs if not xp or vista.
And if that doesn't cut it. Then I would guess you have an actual hardware malfunction of the usb ports or reading capabilities of the Hard drive itself.
If any of this is daunting to you then i would get a professional to help you out as it's not for the uninitiated.
Let me know how you get on or if this advice helps.
I take no responsibility for other peoples actions on my advice which are just opinions. So if your not 100 percent sure don't do it.
lynchy
June 2008