from machines, we sell KTA (Kingston Apple RAM)

nope, OEM Apple RAM is not ever sold separately.

KTA is certified to always work on Apple computers...

Personally, I don't care what sales people say, its my Mac... if it has kernel panic or any other RAM problems, I have to fix it...

pls check the CPU.
if your About This Mac reports "Core Duo" then your max RAM is 2GB
if your About This Mac reports "Core 2 Duo" only then is your max RAM 3GB

for those using the Santa Rosa (Intel GMA X3100, you have a max RAM of 4 GB, can safely ignore the above instructions

I'm quite sure of my info.
@ Jason, go thru the spec for each and every model, back to 2006 and you'll see.

I've tried installing more than 2GB on Core Duo, it doesn't detect.
I've tried installing more than 3GB on Core2 Duo, also doesn't detect.

Not tried installing more than 2x 2GB (4GB total) on Penryn, mainly cos those chips are crazy expensive.
Anyone wanna experiment, my Penryn 2.4 is ready

btw, Tiger is already a 64-bit OS... the memory is not only bound by system software, also bound by the hardware. Which is why even installing Snow Leopard will not help the Core Duo to have more RAM... the CoreDuo has a chipset (hardware) limitation, keeping the RAM at 2GB

@ Jason
machines can't take back the RAM cos of warranty issues... the RAM stick doesn't have a separate warranty, its warranty is only as part of the Mac you purchased.

Apple = quite strict on this