I bought a new USB drive to use with Mountain Lion's ability to target more than one disk for Time Machine backups. When I first set up the drive, I decided to try encrypting it, which I'm now regretting. It seemed really slow, Finder was telling me that the disk had multiple volumes when I tried to eject, and I decided to go back to non-encrypted. I tried the Finder command to reverse the encryption, but after letting my Mac sit all day it was still trying. I wanted to wipe the physical disk and start over, but DiskUtility doesn't seem to have a way to do this. I tried various diskutil commands in Terminal, but it keeps failing with weird errors. What else can I do to just erase this disk and start over again?