You need to use something like 7zip to extract the .gz file into an IMG file, then you use win32diskimager to write the .IMG file to the SD card.
https://github.com/retropie/RetroPie-Setup/wiki/First-Installation-(RetroPie-SD-Image-2.6)
You need to use something like 7zip to extract the .gz file into an IMG file, then you use win32diskimager to write the .IMG file to the SD card.
https://github.com/retropie/RetroPie-Setup/wiki/First-Installation-(RetroPie-SD-Image-2.6)