MMC and policy editor errors and problems

Hello there, I created an account just to ask for help. Sorry for that.

All right, so I was trying to setup a standard account with all access into the secondary drive denied and it seemed -not sure really- that it shared a "user group" with my main admin account, and so it would deny it access too, so I searched for a way to change the user group. I found a guide and proceeded to follow it, but it required that I go to "Local Users and Groups" in the left panel of the Microsoft Management Console. But to my total confusion it wasn't there as can be seen in this image:



But that window looked familiar and I opened a link I have to the Local Group Policy Editor, which opened with this error -that appears a second time after I click ok-:



So I'd appreciate it a lot of you guys could help me with these 3 matters:

1- Fixing the Microsoft Management Console from not showing "Local Users and Groups", and possibly other stuff in the left panel.
2- Fixing the Local Group Policy Editor from showing that error.
3- My original purpose of denying a standard account access to a secondary drive. The point is to run some executables "as" that account, so that it cannot access that drive. Of course any subprocess or any other executable created or ran by the first, shouldn't be able to access that drive either.

Thanks so much.

Sorry to insist but I'm sure somebody here should know how to fix the Microsoft Management Console or the Local Group Policy Editor. It's very important for me and other than that this Windows install is perfectly clean and working.