Well you do need to have the assets files (models, textures, icons, sounds etc) on the same pc iirc (in the same folder or subfolder of the game exe or in a fixed folder or such but the latter is not recommended). If you want to hide your assets, you can:
- buy pro (maybe from someone on this forum) and mark the 'resources' option in the compiler to put (almost) all of your assets in 1 file. This also looks a bit more professional/clean imo.
- obfuscate the code with a program.
- if it's purely for the looks than just put the assets in a subfolder.

Anyway I wouldn't worry to much about others using your stuff, especially the .mdl files since they first need to go through the proces of converting them since not many still use gs3d.

Another idea might be if you use a remote access program instead to put the bulk of your assets in a fixed folder where others who remote access your pc/game dont have access (should work I think). But this is ofcourse only a possible solution for your own pc, not if you want to distribute the game.
Like e.g. with teamviewer you can limit quite a bit of stuff others can do on your pc.