O aye to the op use CCleaner to clean your registry out.
It sounds like your user profile is a wee bit dodgy.
this can happen if you don't log out properly and just kill the machine holding your finger on the power button. Or the machine dies on you a few times.
The best way to test this is by making a new account and seeing if you see the drives when you start using that one. If it does work the simple way is to change to using that account and always make sure you shut the machine down properly allowing it to soft power down.