How to Upgrade iMac RAM (20" and 24" Aluminum): EveryMac.com
Apple iMac (24-inch Penryn)
4GB [2x2GB] DDR2-667 (PC2-5300) RAM Memory Upgrade Kit for The Apple iMac 7, 1 (20-inch, 2.0GHz, MA876LL/A) Intel Core 2 Duo (Genuine A-Tech Brand) at Amazon.com
Tutorial – Installing Windows 10 64-bit on 2007 iMac 7.1 | Joseph Lo's Tech Blog
Apple iMac 7.1 20 Inch All In One Computer 500GB HD 2GHz Intel Core 2 Duo A1224 662225748589 | eBay
Buy iMac - Apple
Identify your iMac model - Apple Support
Can't update iOS. 2008 model iMac running Mountain Lion(?). Old version of Safari will hardly open any websites and can't download chrome due to old OS. Seems to be unable to run