My screen has a big black border around it

Hi No! My name is David. I am a user of Microsoft products like you, and it is a pleasure to greet you.

I'm sorry to hear that you're experiencing this inconvenience with your display, especially after just playing games. I'll do my best to help.

From your description, it sounds like the screen resolution or display settings might have been altered, particularly if you were using key combinations like Ctrl, Shift, etc. Given that you're connected to a TV, there are a few common scenarios that could cause this.

Let's try some initial steps.

This could work for both Windows 10 & 11:

* Right-click on the desktop and choose "Display settings."

* Under the "Scale and layout" section, there's an option called "Resolution." Click on the drop-down menu next to it.

* Try different resolutions from the list to see which one fits your TV best. The recommended setting is usually a good starting point.

* If that doesn't fix it, look for an option below called "Advanced display settings" and ensure the Refresh Rate matches the capabilities of your TV (usually 60Hz for most TVs).

* Click "Apply" and see if the black border is gone.

As additional information, could you please answer the following?

* The brand and model of your graphics card (if any).

* The exact connection type you're using to link your computer to the TV (e.g., HDMI, VGA).

* Whether there were any updates or software installations before this issue arose.

* The specific version of Windows you're using

Let me know if the information has been helpful; if you need further assistance, please respond to the questions I've asked. Regards.