Was working on a Dell PC that had a failed Seagate hard drive. The drive would spin up but could not be detected by the system. I was able to order a new drive and get the PC back up and running. However there were tons of photos and documents that need to be recovered if possible. I found that some Seagate Barracuda 7200.11 hard drives have known firmware bugs. There are two common errors.
0 LBA error: it happens when your BIOS can recognize your HDD at POST moment, but as an 0MB drive.
BSY error: it happens when your HDD enter on a halt state, or BuSY state. In this condition, your HDD will not be recognized by BIOS at POST moment.
The error I encountered was the BSY error, which is recoverable. But it requires connecting to the drives serial interface which is located next to the SATA connector.
I purchased the required RS232-to-TTL Adapter from eBay, followed one of the better sets of directions I found on Google and was able to recover all the data from the drive. [more]
How to recover from BSY error - https://sites.google.com/site/seagatefix/