I recently needed to edit a WIM file, in particular, delete a file in it. At first, I didn’t even know what it was, but it opened in PowerISO. Then, I found out it was another disk imaging format, Windows Imaging Format. [http://en.wikipedia.org/wiki/Windows_Imaging_Format]. Apparently, these images are file-based and not sector-based as in ISOs.
I found a post from Microsoft about it, “Mount and Modify an Image”. [http://technet.microsoft.com/en-us/library/cc766067(v=ws.10).aspx]. Basically, I needed a program called ImageX, which is included in the Windows Automated Installation Kit (AIK) [http://www.microsoft.com/en-us/download/details.aspx?id=5753]. However, the AIK was 1.7 GB! I was glad to find a post about just retrieving ImageX.exe, “Download just imagex.exe (568k)”. [http://tinyapps.org/blog/windows/201204010715_download_imagex.html].
After that, it was just opening CMD with admin privileges and using ImageX to mount the WIM to a writable folder, make the necessary changes, and finally unmounting and committing the changes.