Can the Administrator log into any account?

What activity are you looking to trace/watch?

Interesting - have you considered programs to monitor activity, or perhaps using a proxy that captures activity instead? And no, I take no offense when something really is none of my business :).

The auditing feature in the windows will allow you to do that. Setup auditing for the given user's activity you wish to monitor and the audit trails are recorded in Event Viewer.

In Windows, what is auditing and how do I use it?

Advanced Security Auditing in Windows 7 and Windows Server 2008 R2

For more information on auditing feature please google it.

For online activity, you could use NetNanny or a similar program with parental controls.

3DPiper said:

Not that it's any of your business (no offense), but we have legal custody of a teenager who used several social media outlets to cause a crime.. While I have those sites and programs blocked, he is very tenatious and has already found several workarounds.. We are trying to let him earn privileges on the computer, but need to make sure he isn't doing things he shoudn't or isn't allowed..

Sorry, sometimes we will have people who are trying to hack someone else's computer for whatever reason, boyfriend/girlfriend squabbles etc. We truly aren't trying to pry, just understand.
I don't know if you have a router in use, but it can be configured to block sites by address or maybe keywords. That would work for all accounts on the PC on that router. Then put a password on the router. But since most young'uns are smarter than us, a router reset button would wipe all of that out.
Maybe be a good time to forget privileges, you do the crime, you do the time. Away from the PC that is, no access.