Replacing a bad optical drive with a HDD
My son gave me a MacBook Pro 3,1 that he said had become unusable. I replaced the HDD with a 480 GB SSD and upgraded the RAM from 2GB to 6GB. The optical drive was not working and I wanted to replace it with a HDD. Problem: the optical drive used a PATA connection and large PATA drives are essentially non-existent. The iFixit adapter accepting a SATA drive was a perfect fit.
Opening the laptop was routine. The only tedious part was moving mounting hardware from the optical drive to the adapter. Everything fit perfectly! I put in a 1TB HDD and then used the OS X (El Capitan) terminal to quickly combine the SSD and HDD into a 1.48 TB Fusion Drive. A restoration from the Time Machine completed the transformation. While not a screamer with a decade old processor and FSB and RAM typical of that era, the resulting laptop performs better than new with over 15 times the storage capacity.
Check the required interfaces before starting. While specs always include the capacities or speeds, they often omit the interfaces and the default choices change over time.