I just watched your video. I did had that problem with my Win7 PC. What I did is disabled Windowds Defender and my Anti virus. Im not sure tho which of the two was blocking the installation. Just make sure to enable those two back once you have successfully installed the software. 
Also if you want to install Sansa Firmware updater just to update the firmware, you can always just do the manual update. If you are using a Fuze or Fuze+ and you want to get the Sansa Media Converter through the updater, just use Video4Fuze
