You're welcome; I'll answer your questions in the order you've placed them....
I know about the human condition known as sleepiness. I had heart surgery back in March and all my rhythms are out of wack, so don't be too hard on yourself.
That's what it says"unknown application" because there's too many programs to list, system files are usually well protected and there should be little or no concern of VLC being permanently associated with your chk file; Any of the 7 Raymond tools should be able to tell you what type of file the chk file is, don't miss the vb5 requirements,
if, you use them.
Though an easier way is to right click on the file then properties, look at the location line on the General tab it should give a hint where the file is, if the line looks cut-off or truncated just left-click-hold and wipe to the right to see the rest of the location.
That's how I was hoping you ran the chkdsk, if you continue to have problems, try an elevated SFC /scannow or boot into
advanced boot options and pick "last known good configuration (advanced)" then finish the boot.
Yes it does, but within itself to work with the existing chk files, and these are cleared when chkdsk finishes. Actually any program can generate a .chk file it is how the operating system was designed to police itself, and chkdsk will work with the existing chk files to understand and reset the chk so it disappears. If there are still problems, you will see it/them in the end report.
There might be a hiccup with the VLC association, but honestly I would believe your system ignored it (the association).
Okay with the flash drive, and you're welcome.
My turn,
What happens when you go back to open the chk file that started this?
If VLC does appear by itself with the "always use" box checked, uncheck the box and click OK, that should release the association if it's there.
Even if the "open with" is populated with other programs pick VLC and uncheck the always box, again that should release the chk from VLC.
In both instances the system will try opening the chk file with VLC,
but, release after the try.