You mean moving it into a different drive ( to shorten the path, I assume)?
This should do the trick:
Open your steam launcher\application (the one with store, library, community)
- Select 'steam\settings'
- Select 'downloads'
- Click 'steam library folders'
- Click 'add library folder'
- Select a different drive from the drop down list (same drive is not possible)
- Create a folder if desired (advisable)
- Click 'Select'
After that you go back to your library and right click the M2TW link
- Select 'properties'
- Click on the 'local files' tab and select 'move install folder'
- Select your new destination from the drop down
- Click 'Move Folder'
You get a progress bar which should be the end of the procedure (I didn't want to wait around to copy all 70GB of my M2TW folder).
I would assume all your M2TW desktop shortcuts are screwed now...
The folder gets moved in it's entirety, custom mods and all. The desktop shortcuts need to be adjusted to the new path. The shortening in the path is marginal.
Old path to mods folder if steam is installed into default path (74 chars)
C:\Program Files (x86)\Steam\steamapps\common\Medieval II Total War\mods\
New path to mods folder (57 chars)
F:\Steamlib\steamapps\common\Medieval II Total War\mods\