'via Blog this'So, to the method!
1. Download the RUU of your choice. To test this process to write this guide, I used a Sensation RUU from this page.
2. Open the RUU exe file, and proceed until you get to the page which says 'View Readme'. At that point, stop.
3. Go to your TEMP folder (on Windows 7 it'll be something like : C:\Users\USERNAME\AppData\Local\Temp
4. Look for folders that have lots of characters in that format: "{XXXXXX-XXXX-XXXX-XXXX-XXXXXXXX}". One of the folders will contain two files, and another folder with the same "{XXXXXX-XXXX-XXXX-XXXX-XXXXXXXX}" format. Open that folder.
5. In there, you will see either rom.zip or firmware.zip (depending on the device). Open it with 7-zip (don't even bother using an alternative - 7zip is the best out there), and extract whatever you want (system.img would be a good place to start)
6. The next step (in order to obtain the files from the img is done by either LOOP MOUNTING or EXTRACTING the img (depending on the type of file system). See our guide to loop mounting and rom images in the Advanced Guides section!