Just wanted to state a few things for anyone who’s about to follow this guide. The optical drive for the 2133 iMac is a PATA (IDE) optical drive which has two disadvantages:
1. The HDD caddy you may have order may be SATA instead of PATA, meaning it has a different connector and won’t fit. Ordering a PATA drive shouldn’t be expensive, I ordered mine from China and it worked great.
2. Any SSD you put in the optical drive bay will be massively slowed down by the limitation of IDE/PATA speeds. Speed-wise, it’s much better to put a 2.5” regular hard drive in the optical drive and put an SSD in a 2.5” to 3.5” bracket in the original hard drive’s spot. The original HDD is connected through a SATA cable, and therefore has a faster connection to the motherboard.