I finally managed to get the game downloaded, installed, and to show up in Steam. But now when I press play, the grey box comes up and says “Preparing to launch Black Mesa…”, a brief black square appears, then nothing happens. Any help would be just the greatest.
(BTW thank you development team for making this game.) 
You are in I think the same situation as myself. I’ve figured out what the problem is but have not yet figured out the solution to fixing it. I have my Steam installed on my non-OS drive which has the label of [b]F:[/b]. When I try to run BMS I get a steam promt that says “preparing to launch Black Mesa”. Then I get a quick flash of what I assume is HL2.exe then it shuts down as quickly as it appeared. I then read that installing the mod into the default “C:\Program Files (x86)\Steam\steamapps\sourcemods\BMS” directory works and sure enough the game did finally run(even though steam is on a completely different drive along wish Source SDK) once the installer finished and I left the “Run Black Mesa” checkbox checked on the installer.
However once I quit the game to try and get it to run in a borderless window the game would no longer start up again and I realized it was because Steam was still trying to run the mod in from the steam folder on [b]F:[/b] instead of the working one on [b]C:[/b]. So either I’ve got to figure out a way to make steam use the sourcemods folder on [b]C:[/b], Or make BMS realize the installation is on [b]F:[/b] properly.
Well, all the files are where they are supposed to be. Thank you for your reply though! I’ve tried a bunch of different things but it still goes to the black box then disappears. Does anybody else have a solution to this problem?
I have had this same problem since last night. I also happened to use windowed mode and played for a bit before exiting. Since then I have had the exact problem described. I am having trouble locating the config files for screen mode and I want to check to see if switching back to full screen mode would fix the problem
Add -fs and/or -fullscreen to the launch options. Fixed it for me.
After finding that I could not launch any other games from Steam, I determined my problem stemmed from deeper rooted issues. I did not mention that I am running Windows 7 on a Mac via Boot Camp, so I needed to install updates. In addition, I needed to install drivers for the graphics card and DirectX. The problem has been solved.
AND NOW I’M PLAYIN’ BLACK MESA WOOOO
Thanks for your help!
Wow after maybe 3 hours trying to get this to work, messing with DLLs and changing gameids, and whatnot. Something as simple as just forcing the game to go fullscreen finally fixes it. Thanks a lot dude.
Founded in 2004, Leakfree.org became one of the first online communities dedicated to Valve’s Source engine development. It is more famously known for the formation of Black Mesa: Source under the 'Leakfree Modification Team' handle in September 2004.