A really dumb issue in Windows 7 popped up on my dad's computer recently and took quite some time to fix. I was migrating some files across the network from his old laptop to his new laptop and bam -- suddenly explorer windows disappeared, all icons on the dock turned into white, and trying to run any program (including cmd, notepad, regedit, regsvr32, control panel, etc.) or open a new explorer windows gave me errors like this:

No such interface supported.

The parameter is incorrect.

Explorer.EXE Unspecified error

This file does not have a program associated with it for performing this action.

Anyways, after trying the solutions offered through searching Google, such as re-registering .dll's, addind a new user from the command line (which is really easy! boot in safe mode with command prompt and type "net user username password /add"), and other methods that have apparently worked for others, the only solution I could find was to reboot, hold f8, choose system recover, and do a System Restore to a couple days ago.

Bummer.