iMAC 24" Mid 2007 Intel Core 2 Duo 2.8GHz 4GB Ram 500 HD Radeon 2600 (A1225) | eBay
A-Tech for Apple 6GB Kit (1x2GB + 1x4GB) DDR2 667MHz PC2-5300 200-pin SODIMM for MacBook (Late 2007, Early 2008, Early 2009), MacBook Pro (Mid 2007, Early 2008), iMac (Mid 2007) - Memory RAM Upgrade at Amazon.com
Memory Upgrades for Apple iMac 2007 - Up to 6GB
Install memory in an iMac - Apple Support
Apple A1225 24-inch iMac 7.1 Core 2 Duo 2.4GHz 320GB HD 2GB RAM Mid-2007 MA878LL | RecycledGoods.com