Deciphering Event Viewer Users

A company delivered a replacement laptop today, the second time they've delivered a "new" laptop that is not indeed new. On the previous machine we found the ID cards for an entire division of another states State Police. This time they've wiped the files, but I see over a year of activity in event viewer. Of course since the old users have been deleted all I get in the User field is a long segragated string of numbers and letters (S-1...)

Does anyone know of a way to decipher these back to their original names? I'd like too try and build a bit more evidence before we take this too our Secretary of State's office.

Thanks,

Chris Kizziar