Toshiba MK2555GSXF will not install in A1181

Actually not that long ago I just figured out the answer. I was doubting myself thinking it was an incompatible hard drive because I was swapping it with my new macbook which you might think is odd, but my old macbook I had just replaced the 60GB hard drive with a brand new 500GB hard drive and that one was working in the A1181 and I wanted to use the 500GB hard drive in the new macbook that only had 250GB. What I found is that my old 2006 A1181 is quite different in layout and design than my new macbook and that made me doubt myself.

Long story short. I went back to opening back up because clearly it wasn't reading the drive and that just gave me the gut feeling that it wasn't completely connected. I didn't think it was the connector because the hard drive I just took out of it was just fine. Add to it that there are some differences in the fact that the hard drive installation in the new macbooks require 4 set screws (one on each corner) and then it is screwed in place where as the A1181 hard drive configuration actually showed two set screws from what I remembered and it slid in place and locked in. I wasn't doing this installation alone. I took the hard drive out of the new one and handed it to my husband who took all the set screws out and slid it in, but it was rather loose and didn't connect so then I added the two set screws and it went in but more snug then what I remembered but either way it went in and everything closed up. Looking back very clearly at pictures of the installation process I looked at the hard drive just as it was being installed and looked at the contactors to see if they were facing up going in or facing down and they were facing up. I pulled the hard drive back out and LOOKY THERE!!! the contactors were facing down. I flipped that bad boy around and it slid in and locked in place. I turned on the computer expecting to maybe have to reinstall an operating system and no. Started up and all the system files and preferences loaded on the old mac. Now, ironically I am reformatting so that I can pass it on to someone else. Thank you so much for getting back to me cause if I was still struggling with this - your info would have been very helpful. Thank you for your time.!!! Really appreciated.

Heather