You're already getting a good deal as it is..and you didnt loose any money..why are you labelling him a "bad one" but you say you don't wanna bash? I'm sure fil was being honest when he said the computer was taken from a running car but he can't/doesn't have time to flag down the next e30 he sees and make sure it runs 100 percent fine!
I don't understand how this was a bad transaction. No money was exchanged, he let you try the computer and it didn't work and you didn't buy it and he took it back. suck up your loss and keep looking for the computer IMHO.