this is also the first thing that came to my mind, keeping the old wallet in his desktop, it means OP's friend is holding something, it's possible that he has an investment held there.
~snip~
We can guess as much as we want, but in the end it may just be a wallet that contains nothing. The man was curious and downloaded the BTC wallet, after some time he apparently deleted it and the wallet file remained. It was a very different time than today with a lot of doubt in BTC, and about seventy times less price than today.