If gadgets aren't starting it's because you turned UAC all the way off.
There's no "fix explorer.exe" patch. If it isn't working, it's because it's beta software.
To become full admin, type "cmd" into the search in start menu, right click the cmd file, run as admin.
Then, type "net user administrator activate:yes" without the quotes and hit enter. It'll elevate you to admin.
Reg entries are locked for the most part.
As for the DVD player, no idea. Might just be a bad connection?