Which graphic card for imac mid 2007??

I have the same Imac and have taken it apart. I also have pictures of the video card removed fromt the slot on the motherboard. Also, refer to this ifixit guide:

http://www.ifixit.com/Guide/iMac+Intel+20-Inch+EMC+2133+and+2210+Video+Card+Repl acement/1014

that shows how to remove the video card from a mid 2007 Imac (20 inch LCD).

Welcome to Apple Support Communities

The Mid 2007 iMac has got the graphic card soldered onto the logic board, so you can't replace it without replacing the logic board. Also, your computer needs a specific logic board, so it will make impossible the task to replace the graphic card. I don't recommend you to try that

To add to Mende 1's response, if replacing your iMac's GPU was,possible, it can only be replaced by whatever optional GPU was available for your iMac's model year. No other newer GPU will ever work in your iMac.

iMac's are all-in-one conputers made with no user replaceable/upgradeable parts other than user replaceable RAM.

So, there is no viable way to service and update your iMac's GPU.

If you need a better, faster iMac, then you need to either look and purchase a newer model iMac or look at the brand new iMacs.

Other than this, you are out of luck with installing a better, faster GPU.

I have the exact same model of Imac. The video card is in a slot and can be removed from the motherboard. The problem is getting something compatible. Apple refuses to sell me a card and insists that I take the computer in for repair.

While your latter statement is correct, Apple only sells parts to AASP's and not to the general public that is their policy. However your former remark is incorrect.

Apple does not supply the video card independent of the main logic board, at any rate your argument is moot because the parts are unavailable to end users unless you can find one used somewhere.