Huh? You sold the computer and agreed to provide some sort of "services" What did you get in return? Or did you mean to write that you bought a computer? For the time being, I'll assume that to be the case.
The other party could, in theory, report what happened to the police and claim that you never intended to perform and, therefore, committed fraud. Whether the cops buy into that is anyone's guess. Beyond that, this isn't a criminal issue.

