Problem with installation

Hello

So i ve been away for a long time and i never was the skilled person with computer science. I tried to instal the mod and followed all the paces, but when i try to launch the game a i click select the mod but it won't launch, the following message will appear " Error running 'medieval2.exe': the system could not find the file.

Can anyone explain me the reason of this bug ? As i said before i m not skilled with computer so bare that in mind.

Where did you install the mod?

on Disk D. Since C i used for work related stuff and the disk D is the one with the largest space. I don't understand what i m doing wrong. I ve a steam folder on Programs 86 but i don t have anything there, all the games are installed on the steam folder located at Disk D