Just added a 256GB Crucial M4 to my 2010 iMac using OEM parts. No issues at all. Not too difficult of a process if you take your time. I also found that taking pictures as you go helps you put everything back together like new. I highly recommend following this guide: http://www.twam.info/hardware/apple/installing-additional-ssd-in-mid-2010-27-imac I also referred to the official service manual. The instructions and diagrams are very good: http://ifix.me/Apple Service Manuals/imac/iMac27_Mid2010.pdf These are the 3 parts you need. Got all 3 on eBay for ~$53 shipped. Power Cable: 922-9531 Mounting Kit: 922-9485 SATA Cable: 922-9538 You will also need 4 screws to mount the SSD to the bracket. If you follow the guide above, he doesn't mention you need this until after you've already ripped apart your iMac so make sure you have some handy before starting. I did the same thing he did which was remove them from a old hard drive. I believe what you want are (4) T8, 3mm x 0.5mm x 3.0mm screws (#922-9927 if you must buy "apple" screws) and it just so happens that the screws on an old hard drive was exactly that. Here's some pictures: Started with this To this Just to add this and back to this If you only want to replace the HDD with a SSD, no need to completely take apart your iMac. You only need to remove the screen and you have direct access to the HDD. Make sure you short the HDD temp sensor (apple part #922-9628) or your HD fans will spin up to max. For the folks purchased their iMacs with the SSD+HDD config, what does Apple name the HDD (e.g. Machintosh HD)?