|If you are able to run the 'Recovery Console' and it sees the drive, it might be worth a try to do a fixmbr. Or it might be necessary to use it to repartition/format the drive. I've had to do that when I've had this problem. But I was able to access the drive on another system.|
(edit) I'm not sure if the recovery console can access a USB drive. You might have to try connecting the drive internally.
If the recovery Console doesn't see the drive, that's a problem. If one of the manufacturer's diagnostic utilities has an option to partition and format the drive, you could use it.
You could try a file recovery program to save some of your data.