0. Make a folder for your Mdls and one for you Smds
1. Install all the requirments!
2. Find your steamapps folder. It should be under (C:\Program Files (x86) [x86 is not needed] \steam\steamapps) Make a shortcut to this file, you'll be using it a lot more often than you think.
3. There are a lot of GCF files with what looks to be a purple icon next to each one. (I56.tinypic.com) Open up a GCF file that is common to the game models you want.
Example: If you want Antlions, look under Source Models. If you want Heavy Weapons Guy, look under Team Fortress 2 Materials (It used to be under the models folder, but Valve confused us). And maybe you want a CSS model, look under Counter Strike Source Shared.
a.) Once you find the MDL you want, copy the other files that look the same around it (dx80,dx90, etc) (I54.tinypic.com) Click and drag all those files to your folder you made for MDLS. If you copied a JPG picture, delete it. It's not needed.
b.) If you're bringing in a model from team fortress, it won't work unless you do one simple thing. Open up the MDL file in a notepad or notepad ++ (<--- reccomended) and change the very first IDST0 into IDST, and there you go. Now it will work
5. If you've installed the mdldecompiled properly (dragged and dropped it into C:\Program Files (x86)\steam\steamapps\USERNAME\sourcesdk\bin\ep1\bin) this shouldnt a problem. Open up MDLdecompiler and find your MDL file for [Choose Model File] and the place where the SMDs will go [Choose output Directory]. Heres what I'm doing (I52.tinypic.com)
a.) Click Extract and wait for it to say "Completed Dumping Model!". Now go look in your SMDs folder just to make sure at least something is there. Otherwise, Extract it again!
b.) If your Decompiler keeps crashing, then keep doing it more and more. Sooner or later, It WILL obey! lol.
7. Open up 3Ds max (make sure you installed those plugins! both Import and Export!) and click File > Import > (look for you SMDs) > Import!
Then, this window is going to pop up that says Pre-parse options. Just click "Okay". Then, ANOTHER window will pop up with alot of check boxes (I53.tinypic.com). You dont need to click any of them (unless you're doing a TF2 model, which you will have to click on the "Convert from left-handed Coordinate Space").
Wait for your model to open. If it's a big model, there will be a long loading time.
8. YOU DID IT! YAY!
If there is an error such as "Missing VSTLIB.DLL" or something.. there is nothing wrong with the model decompiler. All you have to do is run Source SDK and try to re-run the decompiler. BAM! It works now.