Any module I download off this site that is a .mod (or sometimes .zip) shows up in my folder after download as an MPEG. When I try to load these modules by double-clicking them, Windows Media Player starts and I get an error message telling me why it won’t run on Media Player.
Just rename the .mod files to .vmod and double-clicking should work (Vassal 3.1 and later).
The Zip files ‘should’ contain a .mod or .vmod inside them, if so, rename it to .vmod. If not, then just rename the .zip file to .vmod.
You can open any module, regardless of name by first starting up the Vassal Module Manager (Click on the Vassal shortcut instead of double clicking on the module). Then File → Open Module and navigate the the module file.
The .mod extension is used by Windows Media Player to identify movie files. Vassal modules have historically also used that extension. Because of this conflict, new modules should use a .vmod extension. But some of the older files have not been updated yet. They really are Vassal modules, but the computer gets confused because another program uses the same extension to mean something different.