Assuming you have collected the ISO from Forrest (~7.5GB)

1. Load ISO
2. Run Installer (Should Autorun)
3. After picking the install directory and hitting install you will be prompted for the SimPack location, it will say this...
C:\Users\*user*\local\temp\supreme commander 2_disk1_0.sid
replace C:\Users\*user*\local\temp\
with the drive letter of your virtual drive (i.e. E:\, or F:\)
so it should look like this
E:\supreme commander 2_disk1_0.sid
it may ask again at the end, do the same thing
4. Explore to the DVD in the virtual drive and open the folder Razor 1911
5. Merge the contents of this folder with the root of the install directory (Merge it\Over-wright everything with the new contents, should be about 3.03GB of data)
6. Blam-O your done, I'm sure most of you wont read this step for step and will mess up something, please prove me wrong

*** EDIT ***
This is for the network mode patch
1. I will push the patch to your systems for install
2. Take the 2 files and put them in \*Supreme Commander 2 install directory*\Bin\ and overwrite the 2 files there
3. Right click on "steam_api.dll" and select properties
4. Make the file "Read Only"
Done! Steam will say your playing some other game, but it wont be an issue