Windows 10 How do I lock / limit another user's access to my folders?

I've got a media / gaming PC setup in my living room, with two accounts on it; mine, a password-protected administrator, and a regular user, called "Steam".

Since I installed Windows on a 120GB SSD, I decided to put my account's folders in another drive. These consists of anything from media, pictures, to work-related files and personal documents.

I have the "Steam" account set up the same way.

The problem is that the Steam account can access my files and folders, and doesn't ask for my account password, as far as I can tell.

Ideally, the Steam user would have read-only access to my videos and pictures, while having zero access to my files and folders. The folders do not have the "Share" option ticked.

How do I do this?

Have a look at some of the File and Folder permissions settings. Right click on the files/folders you don't want 'Steam' to access, click the 'Security' tab, then 'Edit' under permissions. Then navigate through the list of users displayed, select 'Steam', and select 'Deny' under 'Full Access'. Hopefully the website I linked should help if you get stuck.