Who was the last logged in user?

I'm going through the computers that are older than three years to have them
exchanged. I have a list of computer names and user names, the year is part
of the computer name and I can ping some of the computers.

But the list is old and hasn't been updated for a while. I need to know who
are using the computers and when. Is there a way in Active Directory to see
who is currently logged in to a computer, or, if it's not being used for the
moment, who was the last logged in user and when?

Or is there a freeware tool that I could use?