That won't work on the first gen Apple TV.
You need to hope that the seller left the partitions intact. If he didn't, you're going to have a really hard restoring the Apple TV OS. Try starting it up in recovery mode. I don't remember the correct remote button sequence for it. If it does startup in recovery mode, just restore it. If it doesn't after a few attempts, then the partitions are no longer there and you'll have to pull the Apple TV's hard drive and restore them.