If you read the response from the record industry, Richard Altman is not an innocent bystander. According to the RIAA he has reinstalled Windows on his mom's computer several times and he was the one who delivered his mom's computer's hard drive to the RIAA. It is not like he has not been involved
The RIAA says that the hard drive they have is not the hard drive that was attached to the computer they are looking for, so they are looking at Richard Altman's computer equipment to see if he has the information they want.
Do they have probable cause to do this? I don't think so, but that is their argument.