Re: UAC and windows 10
It's not so much disabling UAC (not really recommended unless you know what you are doing - can be highly irritating to be asked every time you install a mod but has no direct effect otherwsie) then disabling the virtual store for the game. The virtual store makes copies of files and redirects to them (afaik) thereby preventing changes to the original to take effect. While a nifty way to stop nasties doing their business it's a pain for mods.
Check this tutorial from step 3 how to disable it for M2TW only. Delete any M2TW directory in the virtual store folder once you are finished.