Wow-wow-wow ... To begin with, I would like to thank all those who are not indifferent, because there are really a lot of answers!
Believe it or not, I’m apparently so stupid that the very first hint helped me, namely, to run "Truckers MP" with administrator permissions... This is the simplest move that I should have done myself, according to the idea, but I just did not guess!
Once again, thanks to everyone who wanted to help me in such a simple situation!