How to properly restrict access of Another User or a Guest Account on all the active drives on my Windows 10 pro

Trusted user account is not a user that is a physical person on your PC.

Forget the registry, you are not doing anything in there that is going to change anything.

I Think you are a bit confused and making this more difficult than it is.

Starting with C:\OS drive. Nobody has access to your user account. Only public is shared. So the only thing left is

C:\Program Files

C:\Program Files (x86)

C:\Windows

For these 3 above, remove users, guest and administrators and add your user name in the list full control. But you need to take ownership first so you are able to do this.

I have no idea why you would have SID S-1-5-21 ………… as the owner of any drive. You need to take ownership of them or change to system for owner. This will not cause Windows apps, features and services to stop opening up as well like the Start menu, Action Center, etc. Impossible.

When taking ownership, the key is the users in the list and the permissions they are granted. But by you taking ownership, gives you the ability to assign users and their permissions.

Now for any other partitions or drives, removing trusted installer does not cause any negative effect. Removing all users on drives also has no effect. You Take ownership of them and add your user name in the user list with full permissions.

You simply take ownership of each drive or partition, disable inheritance and add yourself .

For additional drives, nobody can access them over the network from other PC's or devices unless you select advanced sharing and share them.

I share 6 drives with up to 6 PC's. If you do not select a drive to share, then it is not shared across your network.

However, users on the same PC, they will have access unless you change ownership and/or permissions for users in the security settings.

My advice is to take ownership of the drives, remove all users in the list, and then add only yourself with full permissions.

How to share:

https://answers.microsoft.com/en-us/windows/forum/windows_10-networking/connecting-pcs-and-users-for-sharing/fb92e439-5dbc-4367-9857-1ef360e9ffdf

How to take ownership of any item and set users or permissions per item.

How to take ownership of any item:

Right Click on any Item>>Properties>>Security Tab>>Advanced

You can see here that TRUSTED INSTALLER is the Owner and all the user names listed below that can run Disk Cleanup.

Now you take Ownership of the Item:

Now you select CHANGE next to OWNER.

Advanced>>Find Now>>Select your user account name in the list>>OK

Apply>>Verify OK. Now you are the Owner of that file cleanmgr.exe.

Now select Disable Inheritance.

(This removes all the users in the list. Enabling it again will replace them back into the list)

If it does not remove them, then manually remove each of them.

Now you MUST ADD Your Name to the User List:

Now select ADD>>Select a Principle>>Advanced>>Find Now>>Select your user account name in the list>>OK>>OK

Now select full control permissions box>>OK

Now you are the owner and the only user on the list with full permissions for Disk Cleanup..

RESTART PC

I share 6 drives with up to 6 PC's. If you do not select a drive to share, then it is not shared across your network.

However, users on the same PC, they will have access unless you change ownership and/or permissions for users in the security settings.

My advice is to take ownership of the drives, remove all users in the list, and then add only yourself with full permissions.

How to share:

https://answers.microsoft.com/en-us/windows/forum/windows_10-networking/connecting-pcs-and-users-for-sharing/fb92e439-5dbc-4367-9857-1ef360e9ffdf

How to take ownership of any item and set users or permissions per item.

How to take ownership of any item:

Right Click on any Item>>Properties>>Security Tab>>Advanced

You can see here that TRUSTED INSTALLER is the Owner and all the user names listed below that can run Disk Cleanup.

Now you take Ownership of the Item:

Now you select CHANGE next to OWNER.

Advanced>>Find Now>>Select your user account name in the list>>OK

Apply>>Verify OK. Now you are the Owner of that file cleanmgr.exe.

Now select Disable Inheritance.

(This removes all the users in the list. Enabling it again will replace them back into the list)

If it does not remove them, then manually remove each of them.

Now you MUST ADD Your Name to the User List:

Now select ADD>>Select a Principle>>Advanced>>Find Now>>Select your user account name in the list>>OK>>OK

Now select full control permissions box>>OK

Now you are the owner and the only user on the list with full permissions for Disk Cleanup..

RESTART PC

Thank you Seahawk.

But Here I'm trying to restrict access of any other User (Guest or Admin) to the drive partitions available on the system.

I can put restrictions on an app or apps but it'd just take a lot of time to as it's not a batch operation.

Secondly, this is what I'm talking about if I add my local admin account by removing all the other User profiles from C: drive for example to take and restrict access to it, It'd make the Windows apps, features and services stop opening up as well like the Start menu, Action Center, etc for me as well.

Last time removing Trusted Installer profile wrecked the system.

These are the Current profiles on the drives and I'm just not sure which ones to remove to test it out again.

The SID account on the drives also doesn't match with Mine's in the Registry :

Thank you.