Just saved my friend's post editing career
My friend's 13 inch MacBook Pro (mid 2009) started to give random write errors, then began to error while booting, until it wouldn't boot altogether. Initially, I thought it was the hard drive, but it was a recent upgrade, so I found it odd. I slapped in another hard drive, but the installer couldnt find it. I began to suspect the internal SATA cable, did my research, and it seems this problem is commonplace. I used a SATA to USB converter Cale to check if the hard drive was readable externally, and it worked perfectly. Yep, it was the cable.
As soon as the cable was on its way here, I opened up the MacBook Pro,, disconnected the battery cable, took out the hard drive and removed the cable, very easily. When the cable arrived, I slapped it in, seated and secured the hard drive, reconnected the battery, and screwed the cover back. Computer booted up like if nothing had ever happened. So, my friend got back to his TV post production gig.
A plastic card like a credit card replaces the spudger for removing the battery cable perfectly. Use a good quality screwdriver unless you want damaged screw heads, but that's an obvious advise.