Okay, so I'm fairly heavy into Windows gaming, and a few years ago I was introduced to a really cool first-person shooter called Nexuiz. A free copy of it (or license, technically) was bundled with a video card that I bought, and I activated it through Steam.
I thought it was great. Really nice visuals, cool weapons, fun gameplay. But then something happened after a while -- it stopped working. In fact, it wouldn't start up at all. What a bummer!
Through research, however, I learned that the publisher may have shut down or something (or abandoned the game), and the reason the game would no longer run is because it was trying to ping its server. But there was a workaround -- people suggested to simply disconnect your Internet connection prior to launching the game, and then re-connect it when you were done.
Okay, but then I read about an even better idea: Go into Windows' firewall settings and create a policy that blocks the game's executable file from trying to go online in the first place. Brilliant!
And it's what I've done, and it works.
I'm not an expert certified network admin or anything, so sometimes going into settings like that can be a bit daunting. But as long as you are on at least Windows 7, just search for the "Windows Firewall with Advanced Security" applet and run it. Then you have to create an "outbound rule" for the Nexuiz executable program file. Under Steam, it's going to be located in the following directory:
Your screen eventually will look a lot like the screenshot here, which is from my system (I named the rule "Nexuiz Internet Block"):
Most of the settings, like "Protocol" and all the rest that are off to the right that you can't see in this screenshot I have set to "Any." And as long as you have "Enabled" set to "Yes" and "Action" set to "Block," this firewall rule should have the same effect as unplugging your Internet connection, but just on this one particular file.
Personally I like this solution better -- it doesn't require that I unplug anything at all, and the game obeys the rule, and continues to work. Of course, I just like to play in single-player mode against bots. Online multiplayer is obviously not going to work, so I hate to disappoint you there.
But . . . this is better than nothing. So happy gaming. :-)