Well, it all depends on how well you want the data erased. From the sounds of it you are worried about the authorities?
If this is the case, and the fallout of having any data left on the drive is too great, destroy the drive.....is your freedom worth 200 bucks?
Anyhow, if you're just worried about your spouse or SO finding stuff on it, then just reformat it and don't ever let her get her hands on it.
The data recovery methods described here cost upwards of a grand. I know, I contacted some companies when a drive of mine crashed. They remove each disc inside the drive and copy it, and descramble it.