Oh boy, I've got a big problem. Files on hard drive will not open

Suddenly a great many of my saved files (audio only, video with audio and photos) will not open.

Instead I get a popup that says "Windows cannot find (followed by the original file name). Make sure you typed the name correctly, and then try again."

What the heck could be going on ? How do I correct it ?

I'm using Windows 10, fully updated.

Just saw this, but I'm currently traveling. Hopefully you can get help here, but it will be over a week before I can get to this.

hoosier, I am sorry but I know nothing about W10.  Maybe Buffalo or Carskick will pop in. Scuzzy will be back early Oct. 
Edit: What kind of a drive is the one in question? Type, not brand.

Please tell me what you mean by type of drive ?

I have a 310S Lenovo computer and many files on main driver and two external drives will not open

If it's happening on several drives then it's more likely to be a Windows problem than a problem with the actual data.  As a test, can you try one of the external drives on another computer?

Is it just the media files that won't open?

After further review it seems

I cannot open jpg, PNG or GIF files

But, no problem opening text, MP4, WMP, WPS-PDF or PPT files

Because of virus, I don't have ready access to another computer

P.S. I'm using Windows 10, 1909 64x version

Try right-clicking on one of the files, and select "Open with". Choose one of the programs from the list and see if that resolves it. "Photos" is normally the default Windows 10 program for those files.

I did not find "Photos" as an "Open With" choice

I did choose "Paint" and was able to open jpg, PNG, GIF and Chrome HTML Documents files

Is there any downside to using "Paint" ?

If not, how can I make "Paint" the default choice for these files ?

Photos is the default graphics program in Windows 10. Apparently the program either got uninstalled or got corrupted, causing the problem you described.

You can choose whatever you like as default. The downside is that whatever you choose may not be the best option for viewing photos. Paint will work, but it's an editor, not a viewer. You may want to reinstall Photos, or possibly another photo viewer that will get the job done.

To select a default program (for any file type):

1. Right click the file
2. Hover over "Open with" and then select "Choose another app" at the bottom
3. Select your preferred app, and then check "Always use this app to open .JPG files"

You can also click your Windows Start button, select Settings >>> Apps >>> Default apps

You could try this?

https://www.winhelponline.com/blog/reinstall-photos-app-windows-10/

I've made Paint my default viewer (thanks scuzzy)

In searching for the Microsoft Photo app, it seemed to be called TWINUI when I looked for "Open With" options.

I'm already presented with two TWINUI buttons if I right click on a photo, but neither lets me open files.

Pursuing buffalo's tip seemed to get me into waters over my head. So, for the present, I believe I will make do with Paint. Thanks for replies all