2GB DDR2 800MHz RAM Memory Upgrade for Apple iMac Core 2 Duo 24-inch (Early 2008) (PARTS-QUICK) - Walmart.com
Amazon.com: Original Graphics Card for Apple iMac Early 2008 24-Inch A1225 Desktop Computer Core 2 Duo 2.8 MB325LL/A, ATI Radeon HD 2600 Pro GDDR3 256MB, GPU Upgrade Video Cards Replacement Spare Parts : Electronics
Install memory in an iMac - Apple Support
Apple iMac 24-inch Early 2009 - 2.66GHz Core 2 Duo Apple RAM Memory | Kingston
Install memory in an iMac - Apple Support
How to Upgrade iMac RAM (20" and 24" Aluminum): EveryMac.com