Flashing a new image shouldn't affect the hard drive. I suggest first you should disconnect the receiver, from the mains, remove the top cover, and check to see if a connection has come loose.
If it hasn't you might have to remove the hard drive, from your receiver, and check it on a PC, this is very easy as they only use SATA connectors and usually just involves removing the side panel, from a PC, plugging it in, then re-connecting the power cable, to the PC, starting it up normally, and checking to see if the second hard drive is recognised.
Hmm I will try it thanks but when I connect the hard drive to the receiver the blue light on the hdd lights up which to me suggests that it is connecting ok. Obviously though something is not right.