For space, you could transfer data to another PC, while reading the bad hard drive. What i think would be a huge problem would be speed of the microcontroller to read lets say data from a 6 GB hard drive.
At maximum possible baud rate to send retrieved info to a good hard drive
115200 bps. IT would take 6 days nonstop to read and send 6GB of information. Most hard drives these days are 40 GB and 80 GB. I wonder if this reading and sending can be done in parralel to spead things up.
I know of this guy that charges obscene amount of money to retrieve hard drive data that has gone bad. Thats why i was wondering.
I dont know much about microcontrollers that can use USB. perhaps this can speed up the data transfer to a good hard drive?