When was the last time you updated the drivers to your videocard? That might be what's causing it.

they are updated as far I have checked

Sounds like the games you're trying to play might be older titles that the PC considers obsolete. It's possible that a recent system update may have rendered the graphics on those games obsolete and the settings on your computer might have to be changed for your computer to accept those older names. If you run the trouble games as an administrator, it should temporarily make the necessary changes to your settings while you play. That's the only thing I can think if the comp plays skyrim with no problem but can't run an older game like Unreal Tourny

that could be it, I'll try running these as admin

Also, make sure the program you use to split your screens is up to date. We had a split-screen problem a year ago - downloaded the latest version, and it works fine now.

what type of display adapter ( aka graphic card) do you run. sounds like a simple driver issue, might be a conflicting issue with the driver and how windows controls and changes the default monitor .

I hate it when technology goes kerphlooey. Hope you can get it working properly!

Okay, hang on. Next time this happens, don't disable your monitor, but rather, open up your playback devices window by right-clicking on the speaker icon in the lower right hand side of the main monitor (in the task bar). Identify which device is your default audio device, in this case it SHOULD be your monitor.

Try changing the monitor being your default audio output to your TV being your default audio output when your TV is connected. This should solve the issue.

If it doesn't, let me know, and we'll go through a longer list of things that could be going on, but I think that simply that your default audio is your monitor and it's not changing with your display. If all else fails, rebooting with the monitors disconnected but the TV connected should work, but that's kind of a jury-rigged solution and a pain to do and... yeah.