Bug - PC/Assets are sometimes marked as CDI by default

[ehw]

Kinda confusing as sometimes discs are marked as CDI as the system type and sometimes there's nothing. I'm not sure when one kicks in over the other. I'm thinking we might want to have "Unknown" be returned instead. I want to say if the disc has .exes that are actual dos/windows executables (meaning they have the header for them) anywhere on the root of the disc or one subdirectory down we mark it as PC.