Windows 10 User Folders – How to Prevent Other Users from Using D Drive

I solved this problem by slightly changing the procedure I outlined in the question. Basically, instead of clicking "Deny" under "Full Control," I individually selected each permission I wanted to deny. I'm not sure why this works, but it does.

First, I deleted User B and recreated User B, to clear up any confusing and contradictory permissions. Then, I followed this modified procedure.

1. Using an Administrator account, navigate to C:\Users and right-click on the "User A" folder. Select "Properties."

2. In the "User A Properties" window that appears, click the "Security" tab.

3. Click the "Edit..." button to change permissions.

4. I the "Permissions for User B" window that appears, under "Group or User Names," select User B.

5. Under "Permissions for User B", check the box under the "Deny" column for the "Read & Execute," "Modify," "List Folder Contents," "Read," and "Write" rows. Click "OK."

The system should then begin working. The process could take several minutes.

My answer obviously will not answer your question but I will try to explain why it is useless attempt:

This - "I don't want to create more than one user account to solve this." is the most common error. No one educated administrator would work on computer under administrator's account. It used only for administrative tasks, such as program installations or adjusting settings for the whole computer.

If there only one account, it is means it is administrator's account and if somebody has access to it then he/she can revert all of your restriction attempts. It isn't applied to a real humans only, but it applies to a viruses too. If they runs under administrator account, - it isn't your computer anymore.