Yes, it was. But I found a way to fix the problem. (Thanks to google.)
I install all my games on another HDD than the OS'. I had to change the virutal memory allowed to the "Game" HDD following this scheme (http://www.rbrussell.com/2015/02/25/possible-fix-windows-10-running-very-slow/) :
– Open up Control panel
– Type in "Performance" into the search field
– Click "Adjust the appearence and performance of Windows"
(or Right-Click on My PC and select Properties)
– Open Advanced tab and click "change" button
– First uncheck "automatically manage paging file size for all drives"
– Then highlight drive the HDD the game is installed
– Select "System managed size" (Or you can allow the size you want, I think)
– Click “Set” and OK
– Finally Restart your PC and you're done
Now the game launches instantly (1-2 secs delay sometimes). I hope it will continue to work this way.
EDIT : Well, it worked for the five minutes after starting the PC. ._.
EDIT (Again) : When you choose the size, it seems that it works better. I'll test that tommorow, it's about seven in the morning here.