I got a Western Digital 250gb 2.5" Internal Hard drive the other day from Newegg, I then installed it EXACTLY like how the Apple guide said to. I then put in the recovery disks and tried to format the hard drive (It said the hard drive was 1.8tb which was kinda odd...) and then it looked as if it was formatting but then a pop up came up and said "Input/Output error". So I googled it, nothing came up the only thing I could find was about External Hard Drives. Then I called "The Mac Store" (One of those Apple Dealers) and then they said they could erase it manually and that should fix it, so I took it to them today and they said "Oh, we can't fix it, you didn't purchase it from here." If anyone could help and tell me what I should do that would be great!