Ok late yesterday i had a bug after reinstalling win 8.1 RTM that would'nt allow me to change the background on my start menu, after reading tons of posts i found a working work-around to fix this for me and its very simple to do. Step 1: Open Run and type gpedit.msc and press ok. you can right click the start button to do this Step 2: On the left hand side of the new window navigate to User Configuration\ Administrative Templates\ Start Menu and Taskbar Step 3: Double click on Prevent users from customizing their start screen and if its not already done so set it to disabled, it should be set as Not Configured by default. See below: Step 4: Reboot for new settings to take effect. i hope this helps others as this took me a few days to solve as MDL was down and i have no knowledge of any other posts made before i have made my simple guide. Ps i used several programs to change it myself but they all had bad results, some wouldnt even open or install.