Someone from Microsoft keeps hacking into my PC

Right that does it... whoever it is from Microsoft that keeps hacking into my PC and removing YTD video downloader - pack it in!

Hi:

Most of those "YT Video Download Helpers" are classified as at least PUPs, if not worse, by most reputable security applications.
There are many such YT downloader applications out there, some worse than others.
Without knowing the exact name of the application in question, we can only speculate.

I doubt MS is "hacking" your computer. So, unless you have fallen victim to a fake tech support scam, it's more likely that one of your security applications is removing it.
Most allow for exclusions or white-listing.
Not recommended, but if you must keep that program, then that would be how to proceed.

EDIT: ALSO -- just for the record, unless specific rights are provided to download a specific YT video, doing so constitutes copyright infringement and/or piracy: YouTube TERMS

MM