Originally Posted by Sheffield Steve
The THR22 does indeed have a diagnostic mode and it seems to be the same as the HR22.
On boot up a screen pops up for a very short time that says "Running Receiver Self Check". If you hit "select" when that message is shown, it reboots into a comprehensive diagnostic mode which includes three hard drive tests. (One of which is a scan of all the sectors on the disk).
Good info to have, but in the case where you think the drive itself, and not the software on it, needs testing, it's still probably better to take it out, hook it to a PC, and boot with a cd with the drive manufacturer's own diagnostic software on it.
Unless it's a GigaByte brand motherboard in that PC, in which case it's still do-able, but you need to know what precautions to take to prevent the board from writing a Host Protected Area on the drive.