Likely there is nothing of value on the hard drive. The issue with the hard drive is just mis-direction.
Websites he visited are on the ISP logs, not on his computer.
Contacts with others, using EMAIL, are on server logs, not on his computer. Nothing that he wrote or received from anyone is on his computer, unless he specifically 'saved' it to his hard drive.
If you use email, YOUR 'mail' is not stored on your hard drive.