Watch the video again, it never tries to change the word default. It adds a new registry key called "StorageDevicePolicies" then adds a dword value there called WriteProtect, it then shows setting it to 1 to enable writeprotect or 0 to disable.
See this: Link Removed
The page I linked to actually has 2 little registry scripts that you can download then double-click on to invoke. One to enable write and the other to disable. Try downloading and running the enable script. You need to reboot after running the script in order for it to take effect.