Windows 7 - How to enable a password prompt for downloads

I have two user accounts. One is an Administrator account and the other a standard user account for my children.

There previously was a password prompt if you tried to make any changes to the system under the standard user account or download any files.

I am not sure what happened but now there is no password prompt to download and execute files under either account. I have tried to loacate “Local Users and Groups” to change the user settings but it is missing in the Computer Management?

I have even deleted my childrens account and created a new one yet we are still able to make changes to the system and download files under that profile.

I have been through every setting I can think of. Any help would be greatly appreciated!