As someone who works in an electronics store, we'll take returns on any electronic items as long as there is no physical damage. Ive seen people bring back parts because they got the wrong thing, or it didn't fit in their system for some reason, or they changed their mind about it. But I've also seen people bring things back because parts were defective, no POSTing, no booting up, hard drives not starting, fans not working, etc.
As C12Friedman said, theres a lot of troubleshooting that needs to be done to determine a problem and its cause.