It's been a while since I need to do one of this. I think I better document this here for my reference. This is no rocket science.
To mount a WIM file so that you can deploy some custom settings such as additional folders and stuff as part of the OS installation. This is what you do:
1. Install Microsoft Windows AIK.
2. Run a command prompt with elevated privillege in Windows 7
3. Create a directory c:\mounted_images
4. Change directory to c:\Program files\Windows AIK\Tools\x86
5. Imagex.exe /mount Z:\Windows7_Source\Sources\install.wim 1 c:\mounted_images
Once mounted, you should be able to make modification.
6. Imagex.exe /unmount /commit c:\mounted_images
http://technet.microsoft.com/en-us/library/cc766067(WS.10).aspx
