In my macbook?
It depends on your specific model MacBook, and the typical caveat is "For best performance, don't mix sizes; always install two identical memory modules."
http://support.apple.com/kb/ht1651
There is no harm in attempting it.
I was told the motherboard was cracked, so when i did it
It kept ejecting the cd drive even tho It was empty and it never booted up. When I Removed the 512 it operated normally. How can i run the hardware test from disk? Is it possible to replace the "logic" board with 1 from ebay? Its a 2008 macbook duo core
Using Apple Hardware Test
You must remove the firmware password, if one has been set, before you can use AHT.
If you need a new logic board be absolutely certain it is the exact one you require for your exact model MacBook. Buy from a reputable vendor (feedback > 99.5%).
everytime I restart with the D key depressed, it reboots and sounds like a machine gun stickey key. I looked on the instal CD, and only found instructions. How do I remove the firmware password?
Can you boot the Mac from your grey Applications Install DVD? It will be the one with "Apple Hardware Test" or "AHT version xxx" printed directly on it. With the disc inserted, restart while holding the c key to boot from the disc, or the d key to run AHT.
Can i use a 1 gig and a 512 mb ram?
