Post originale di: Dan ,
I suspect your drive cable is bad. Apple had a bad run of cables for this system. Here is the part you will need: [product|IF163-041|MacBook Pro 13" Unibody (Mid 2012) Hard Drive Cable]. Here's the guide you'll need to follow: [guide|10379|MacBook Pro 13" Unibody Mid 2012 Hard Drive Cable Replacement]. I also suspect your original drive is OK. So you might want to see about returning your new drive unless you also wanted to get a bigger drive and that is why you replaced it to start with.