I'm writing this guide because these drives seem to have an extremely high failure rate. My 2008 imac (2.8Ghz intel core 2 duo processor) had the card fail on me not too long ago so I set out to find a solution. There is a lot of conflicting data on whether the graphics card in the imac is replaceable. This stems from the fact that many of the older generation imacs have the GPU soldered to the logic board. This is NOT the case with the 2008 24 inch that has the card mentioned above. It is very difficult to get to. But with planning, patience and care, it can be replaced. Since there don't seem to be any guides for this particular generation and the failure rate of these cards is so high, I figured I'd take the liberty of posting some tips and references for changing this card. I was going to do a step by step guide, but the ifixit guide is pretty much all you need. I replaced my Nvidia 8800 GS with an ATI Radeon HD 2600 Pro. The product number for the ATI card is 661-4663. This card was a direct drop in for the Nvidia Card. I ordered it from memory4less and it came with the heat sink. There are a lot of sites that claim to have this card, but after ordering I got a notice that it was not in stock. Memory4less was more expensive, but the only place I could find that actually HAD it. The ATI card is 256mb as opposed to the 512mb that the Nvidia card has. It's definitely a bummer to downgrade. But the ATI cards seem to be rock solid and I don't notice any performance issues since the switch. It was noted by another poster that some of the ATI cards may cause freezing issues for some users due to a driver problem when using Lion or Mountain Lion. I use snow leopard and I have not personally had this issue. But it is something to be mindful of. Keep in mind, this is NOT a quick fix. It takes a LOT of time and careful handling of sensitive components of the imac. I'm not the most tech savvy person in the world. But I'm very patient and methodological which helped me to get through this with no major issues. I don't have any pictures because at the time I replaced the drive I wasn't planning on making any sort of how-to. I also don't have screwdriver sizes or anything like that. I just had a box full and had to pick out whatever fit. However, I used this ifixit guide for replacing the graphics card in an older intel 20 inch imac.: http://www.ifixit.com/Guide/Installing-iMac-Intel-20-Inch-EMC-2133-and-2210-Video-Card/1014/1 While there are a few small differences in some steps, this guide was extremely helpful for me. If your card already has the heat sink attached to it, as mine did, You only have to go up to step 38( after that it goes into placing the old heat sink on the new card.) This guide also has screwdriver sizes listed. But please note that the screw sizes and placement will not be exact since that guide is for the 20 inch. A few tips: -In order to get the glass panel off my mac, I used two suction cups from GPS stands that I had lying around. If you are careful, you can do it with just one, but two is a bit easier. This is cheaper than buying suction cups for a one time job. -There are probably 10 to 15 DIFFERENT types of screws. Make sure you have a system of keeping track of all the screws and where they went. I printed off pictures of the logic board and numbered every screw I took out then layed the screw on a piece of paper with the number next to it. Some ppl have used baggies to label them. This is very important because even screws that parallel each other can be different sizes. -Avoid touching the LCD panel. I got a few prints on mine and it took like 10 mins of gently wiping with a microfiber cloth before I could get it clean again. -When Rescrewing the LCD panel, don't screw it in too tight or you will get increased backlight bleeding on your display. I had to take the glass off again and readjust the screws. -The LCD Panel is plugged into the logic board. Re-plugging this part in was the most difficult part for me of the whole thing. I had to have my roommate Hold up the panel while I tried to get it plugged in. It's such a strange angle and it's a pain. Fair warning. -Also, compressed air is a must. It'll give your imac a nice cleanin, and will help to keep dust from settling on the LCD or the glass (spray frequently, but be careful!) -The placement of the screws to remove the logic board are somewhat different from the guide. I did have a paper that I printed off and labled which screws I took out, but I threw it away since it was scribbled all over (and, once again, I wasn't planning on writing any guides). -Don't forget to remove and replace the memory before and after taking the computer apart. Along with the ifixit guide, I wrote in a notebook EVERYTHING that I unplugged from the logic board before unscrewing it. In fact I would suggest writing down every step in the entire process so that you can easily work backwards when its time to reassemble. There are a lot of things to unplug. I will list them off here, along with descriptions. I would suggest printing off this list and checking each item off once during disassembly (when you unplug it), then once again during reassembly. This will help to prevent you from forgetting to plug something back in and having to take everything apart again. I'll include the descriptions I wrote in the notebook. They aren't very techie sounding. I kept them very basic so I didn't get mixed up. Some of these are different than the ifixit guide, which is why I am adding the descriptions. I dont know how consistent the 24's are inside, but hopefully this helps. Items unplugged from Logic board/Location on logic board: Left Speaker Wire: Long black wire that leads from the left speaker to the sound card on the right side of the imac. Ambient Temp: four tiny wires connected to a small 4 prong plug goes into the very bottom left corner of the logic board Power Button: Two tiny black wires connected to 2 prong plug. Located Just to the bottom-right of the CPU fan plug CPU Fan: Labeled on motherboard: Located directly above “Ambient Temp” SATA Data Cable: Labeled as “MLB”. Goes into Right/middle/Bottom of Logic board. Just to the left of where Blutooth gets plugged in. DC-In Cable: Large cable/plug with retaining tabs. This is the largest plug on the board. Airport antenna connecters x2: Tiny single wires that pop into the wireless card. Gray goes on top, Black goes on bottom. The wireless card can be identified by the model information and “made in china” written on it. Blutooth Antenna: Tiny single blue wire. Pops into golden slot just like the airport connectors. Located to the left of the watch battery on the right side of the board. Camera Cable Connector: Labeled on board: Slot is just below the wireless card, slightly to the right. The cable is a single thick black wire with 4 small wires (gray, white, light green and blue) coming out and one slightly thicker black wire. The plug is near wireless and blutooth plugs on the board. Right Speaker Wire: Long black wire that goes to sound card. Plug is on top left of soundcard. Optical Drive Fan: Slides out Parallel to the board (rather than being pulled up out) This is located just above the soundcard. It is somewhat covered by the optical drive cable. Optical Drive cable Clip: Screws in with 2 small screws: there is a small chip on the end of the cable. Microphone Cable Connector: Plugs into the sound card just to the left of the Right Speaker Connection. Hard Drive Thermal Sensor: Located at the top of logic board Just under hard drive. Comes out parallel to board. Black & Gray cables intertwined to a 3 prong connector. Optical Drive Thermal Sensor: Right next to hard drive thermal sensor. Two black intertwined wires. 2 prong: Goes in Parallel Hard Drive Fan: Labled: Next to Optical Drive Thermal Sensor. 2 black wires, one brown wire, one gray wire. 4 prong. Goes in parallel. Using these tips and the ifixit guide, you should be able to replace the card without much of issue. As stated, there are some differences in some of the connecters and screws/screw placements. I just eyeballed this for the most part and was able to get through it without any problems. If anyone does decide to attempt this, I would suggest taking pictures and noting differences from the ifixit guide and posting them on here to help anyone else that decides to replace their card. I'll be sure to update this with anything else I might think of. I realize that this is a bit longwinded for not being an actual step by step guide. But I do hope this helps for people who are considering replacing the card.