first of all, are you using the last version of mpc-hc from when the projected closed some years ago or the updated version available from K-Lite?

Second, I believe k-lite offers a reinstall that can reset defaults which might fix the problem.

Third would be to see what windows is using for your display setting and whether the type and resolution are appropriate.

I'm almost positive your problem is not the video player and changing the video player will not solve your problem. People telling you to change the video player don't know what they are doing period. No offense but its the truth. All video players have zoom settings. You just need to adjust them sometimes because the video player doesn't always automatically compensate for your tv and pc resolution settings. It doesn't mean the video player is faulty.

First there is one setting on MPC you can check before messing with the pc settings. It may or may not solve your problem but try this before adjusting pc settings.
Start a video with MPC and pause it then right click with your mouse. Click on - Video Frame - on MPC. You should be using either Normal Size or Stretch to window. I use stretch to window on my 4k laptop and on my 1080p laptop I use Normal size. Also on Video frame click on Aspect Ratio (Scaling). Normally Default Aspect Ratio works for most people. Sometimes 16:9 setting will work better but only change this if default isn't working for you. If this solves your problem ignore the pc settings information I posted below.


Two things on a pc can cause the video zoom  and sometimes its only noticeable when you are playing video.

Go to pc Display settings - resolution settings. Depending on how your tv is setup you may need to adjust resolution.

Another thing that can cause this is in display settings - advanced settings - refresh rate.  A couple times my pc decided on its own to change the refresh rate from 60hz (where it was supposed to be) to 59hz and that little change will mess the video.

On my 1080p laptop refresh rate is 60hz. On my 4k laptop refresh rate is 120hz.

Also one other thing can cause this but this only applies only if the pc you are using has a video card. The laptop I'm using now has an hdmi port for onboard display and a usbc port for the Geforce card.
If you are using a video card (this does not apply to on board display) sometimes you may also need to go into the display scaling and manually adjust the screen size. Video cards generally have a lot more resolution settings than on board display which means more fine tuning.

Why not try another media player like VLC or MPV? I tested this mpc-hc and everything's fine.

Going to full screen has nothing to do with it or the video picture not fitting the screen correctly.  Its similar to when you zoom in on something on your cellphone. When you zoom in on cellphone obviously you cant see the entire screen like you did before zooming in. F11 and full screen has zero bearing to this topic.