Upgrading this iMac's CPU has been tackled at iFixIT. http://www.ifixit.com/Answers/View/53213/CPU+upgrade+2.0GHz+to+2.8Ghz+(+C2D+Extreme+X7900+) What I want to know is can I upgrade my iMac Socket P CPU to a Socket P CPU that has a FSB faster than 800MHz (1066MHz) or TDP that is higher than 35 watts (45 watts)? If I can use a Socket P CPU that has a 1066MHz FSB does that mean I need to buy DDR2-800MHz memory as well? The Socket P CPUs I am thinking of using are the following: Quad-Core Notebook processors 2.53 GHz Core 2 Extreme QX9300 2.27 GHz Core 2 Quad Q9100 2 GHz Core 2 Quad Q9000 Dual-Core Notebook processors 3.07 GHz Core 2 Extreme X9100 2.8 GHz Core 2 Extreme X9000 2.8 GHz Core 2 Extreme X7900 2.6 GHz Core 2 Extreme X7800 3.07 GHz Core 2 Duo T9900 Specs of the Mid-2007 iMac is below. Hardware Overview: Model Name: iMac Model Identifier: iMac7,1 Processor Name: Intel Core 2 Duo Processor Speed: 2 GHz Number of Processors: 1 Total Number of Cores: 2 L2 Cache: 4 MB Memory: 4 GB Bus Speed: 800 MHz Boot ROM Version: IM71.007A.B03 SMC Version (system): 1.20f4 Apple Order No: MA876LL Apple Subfamily: Mid-2007 Apple Model No: A1224 (EMC 2133) Model ID: iMac7,1 Other than the CPU i know I can upgrade the memory to 6GB DDR3-66MHz and plug in a SSD to the SATA 3Gb/s port. I could work on a PATA to SATA optical bay caddy mod but that's too much work I thinks.