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I have a 2010 low end 15" macbook pro.

I got this 1TB seagate expansion portable drive today and wanted to know if it'll fit inside my mbp as a replacement for my current 320GB drive that's almost full.

http://www.seagate.com/www/en-us/products/external/expansion/expansion_portable/

Why are you wasting money by buying an external drive just so you can take out its hard drive and use it as an internal?
Buying an internal drive fresh from the start is much better, and offers better compatibility. Go on Newegg and find a 1TB 2.5" bare drive, make sure its height is 12.5mm and less, and you got yourself a good drive.
 
It's not a waste of money. I want a larger drive in my mbp and use the current drive as an external, thus needing a case to put it in. Where I live it works out cheaper per GB to buy an external and swap the drives than it is to buy a drive and a case on their own.

The drive was thicker than the original but it fit. Its a lot louder than the Hitachi drive I had in it so I swapped them back.
 
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