Encrypting file system prompt? Am I hacked?

Suddenly I get a prompt to save out a key for EFS, but I have never turned on this feature and it's never done this before. I am using windows vista ultimate. Is this normal or is there a problem? A quick google search didn't find virus but there's too many hits to check them all....

I've never turned it on, and it hasn't run. W7 Ultimate x64
The system has to be partitioned when it's set up. Someone must have done that, and turned it on