Question: To add subtitles to a single file I use the following command:

`mkvmerge.exe -o g:\movie01.mkv --default-track 0 --language 0:pl movie01.mkv movie01.srt`

**Where:**

`movie01.mkv` is the name of a video file

`movie01.srt` is the name of a subtitle file (it is always the same as the video file)

`g:\movie01.mkv` is the output file

**How do I run the above-mentioned command for every file in a directory?**

Answer: 
Check its digital signature!
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A freshly installed version of Windows 10 Anniversary Update has an `Explorer.exe` at `C:\Windows\SysWOW64`. It is digitally signed, so even if one byte of it is changed, its digital signature will tell you.

To verify that it is the authentic `Explorer.exe`, check its digital signature by doing the following:

[![How to check digital signatures](https://i.stack.imgur.com/YHq7L.png)](https://i.stack.imgur.com/YHq7L.png)

1. Right-click on the Explorer.exe and select "Properties..."
2. From the "Properties" dialog box, choose the "Digital Signature" tab. (If this tab doesn't exist, then there is no digital signature in the file and that means it is not authentic.)
3. From the signature list, choose the signature and click on "Details".
4. Look at the second line of the dialog box that appears. Does it say "This digital signature is OK"? If it doesn't, the Explorer.exe is not authentic.

Doesn't have to be in your computer
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You can always do the verification in another computer. i.e. copy `explorer.exe` to a flash drive, take it to another computer (or even a virtual machine on another computer), and verify it there.

This action is effective if you fear that your computer is deeply infiltrated by a super-virus that can even alter the result of a digital signature check. Like in the movies! (Of course, in the real world, if such deep infiltration happens, the virus no longer bothers hiding itself because all is already lost and it is already in full control of your system. It is like saying a petty criminal took over POTUS just to remain hidden and has no intention of ruling over the whole US!)
So, as it turns out, it was a virus.

I rebooted my Windows after scanning it to find that it had triggered a `diskpart` on my machine, wiping my hard drive.

I took it to the local computer store, and the guy that worked there said that it would of caused it. (He somehow managed to check logs that were on my motherboard.)

Virus Total said it was a virus and Malwarebytes said it was a virus, but I couldn't remove it.

Ah well, i'll just switch to Linux then :D