Yes, basically PC games send their audio streams out discretely. So you set the game to output surround, its going to send the OS/Audio Hardware 5.1 unique streams of audio info to deal with.
At this point your PC should be set up to pass those 5.1 streams of audio out via the HDMI port you are using, usually an OS setting is configured here in your drivers, perhaps. That's all you want your PC to do, take the audio and send it out on the HDMI cable to your receiver.
Now, assuming your receiver has modern chips inside of it, it should have a setting called "DIRECT" or "MULTICHANNEL".....look in your manual. This is the setting that tells the receiver "Look, don't touch this stuff, just send it to the correct speakers, don't do anything but route it and amplify it". At this point, you *should* get discrete 5.1 surround sound from the game.
If its still problematic, my advice is to just set your receiver to DTS NEO 6 or PRO LOGIC x or whatever the current standards are and use simulated surround sound, most of the time it works just fine.