I was given a A1181 MacBook 13" laptop. (EMC 2139)
Had a completely horked hard drive. 1GB of memory.
Put a 320GB hard drive from an A1226 (EMC 2136) and the 4GB of memory.
Damn thing booted right up like the old computer never had a problem, the OS adapted just fine from the MBP to the MB. Still has the 3GB usable issue.
But for free... that ain't bad.
All in all, I'm happy with it. Now to get the daughter to get her crud off the hard drive, so I can put Linux on the MB.