Replacing macbook hard drive from one running older OS X
This is kinda complex sorry.
So I've got 2 black macbook A1181s, an older one running OS X tiger because of its crappy processor will only support 2GB RAM and a newer one running snow leopard maxed out at 4GB RAM, but the newer one got a S.M.A.R.T error so I've tried replacing the hard drive with the one from the the older one but it won't read it because, I'm told, of the upper memory limit on OS X tiger. I have no install disk because I bought both second hand but is there any way to install snow leopard onto my old hard drive then restore my backups from USB or will I have to buy a new hard drive and install disk? Obviously I can't install the new os with the hard drive in my older macbook because the specs are too low (it's an early 2006 one) so I'm kinda stuck. My question is would using a combination of smaller and larger memory units in my newer macbook make it compatible with the older hard drive and OS X memory specs? And is all of this worth it or should I give up and buy a cheap new PC? Thanks a lot in advance I know it's hard to follow :)
MacBook, Mac OS X (10.6.8)