Dark Messiah in Garry's Mod

I tried asking elsewhere but didn't get much so I'll ask here.

I have a standalone version (or maybe the retail version) of Dark Messiah of Might & Magic, I was going to download the Garry's Mod 10 Standalone before I do that I want to know if my Dark Messiah standalone will work with Garry's Mod 10 (standalone ).

I'm not sure if my Dark Messiah is the retail version so here is a screenshot.
They aren't in the GCFs / NCFs format so they can't be for steam.