Neither Safe nor TrueCrypt would help in this situation. These would protect the data on your hard drive from unauthorized access, but not from being copied. Imagine this scenario: I bring my 60GB LaCie Pocket Drive (USB and Firewire, bus-powered), attach it to the MC computer, and copy the files from Windows Explorer or through MC to my unencrypted drive. Encryption defeated. Now, if they contain a system where you need to authenticate on each file access, that could help, but obviously that would prevent the use of MC on the computer.
AlexB's idea could work, and it would prevent 90% of the "potential infringers", however ...
Just be aware, depending on your configuration with Nero, Limited Users on XP can sometimes access the CD burner. I don't know, because I won't use or buy DRM-protected material (I personally have some issues with the Freedom of Speech and perpetual copyright issues with it), but will MC still let you convert DRM files using the "record from soundcard method" I mentioned (and just learned about) above?