Gawd, I'm getting sick of every second topic here being about this question, so answer time
The answer? Simple
TOOLS REQUIRED
1 x
WC3 Viewer
1 x
WC3 File Converter
1 x Warcraft 3, Frozen Throne
1 x Word Editing program: I use Notepad, but you can use Word Pad if you want
INSTRUCTIONS
1. Make a folder somewhere to keep all of your
WC3 tools, I suggest putting a folder called "Tools" in your
WC3 folder, but your choice. Then download the tools to this folder.
Why can't you put them in the
WC3 folder? Because then you'll screw up
WC3 and the tool
2. Open
WC3 Viewer, click "File, Open MPQ" and select either "
wc3.mpq" or "wc3x.mpq".
wc3.mpq has the original units, and wc3x.mpq has the expansion ones. Neither of them have the Firelord, Tinker or Alchemist, seeing as how those three are in wc3patch.mpq, which you can't open due to its lack of a listfile
3. Find the model you want, and extract it somewhere
4. Use the File Converter to convert the mdx file you just extracted into a mdl file
5. Open the mdl file in notepad/wordpad
6. Find the part where it says "Textures", find the skin that this model uses and change the path to something else for the skin. REMEMBER THIS PATH
7. Save, then convert back to mdx
8. Get open
WC3 World Editor, start a new map and then import the model and the skin. Put the skin in the path you gave it earlier, don't need to do anything for the model
9. If all went well, save and restart, then place the original unit and the one with the changed skin. They should use a different skin.
There, 9 steps to solving this ever-asked about question