Hide extentions for known file types won't work! W8.1 x64

Hello everybody!

I've been facing an issue with my Windows 8.1 x64 OS.
I'm trying to set the option "Hide extentions for known file types" in Folder Options, apply the settings and hit OK. When you open the Folder option again, the "Hide extentions for known file types" flag is off again.
Same thing with "Hidden Files and Folders" option.

I tried changing the value on RegEdit too but it doesn't let me modify it.

Any help?

Thanks in advance.

Boot to Safe Mode, see if you can do it there.

See here: http://www.eightforums.com/tutorials/5245-startup-options-enable-disable-windows-8-a.html

A note: the default installation of Windows is for Don't show hidden files, folders or drives and for Hide extensions for known file types to have the radio buttons checked.