What to do about a bad video card in a 2010 Mac? It seems it was just 2013 when Yan asked a question about a Mac showing a strange display. I'm now getting exactly that display, on a Mac that seems to me to be around the same vintage as Yan's, 2010.

The responses to Yan's question talked about plugging in an external monitor. But if the video card is bad, won't the image in the external monitor be just the same one Yan photographed? In other words, doesn't the video signal to every monitor emerge from the same bad video card?

What can I do to retrieve the files from my Mac without allowing anyone else access to these files? I would be willing to replace the Mac if that would somehow facilitate. Is there really a way to just plug in another monitor, or some other new hardware, into the old Mac? If I have to take the Mac to the shop to replace the video card, will that allow the repair shop access to my files? Is there a way to get the files from the Mac without replacing the video card? What are my options?
This answer is based on the assumption that you've got an iMac, however, the general solutions (not anything iMac specific) presented here will work for virtually any Mac model.

Use Target Disk Mode

If you can boot your computer (even if the screen is dead) put it into Target Disk Mode by booting it while simultaneously holding the T key.  The computers need to be connected by a Thunderbolt or FireWire cable.  The iMacs from this vintage (through late 2011) all came with a FireWire port.  Thunderbolt didn't come onto the scene until 2012.


FireWire Cable
Thunderbolt to Firewire Adapter - Only necessary if using a newer Mac with Thunderbolt ports


Once connected, you can boot the computers and copy the files over.

Remove the Hard Drive

Since your graphic card has died and they are quite expensive on the secondary market, it makes sense to simply extract the drive and connect it to a USB adapter to copy the files over.

The iMacs through late 2011 all came with the removable glass where you could simply use a couple of suction cups to pull the glass off.  The display panel was held in with 12 Torx screws.  Once removed, you have access to all of the components.  Ifixit has an excellent step-by-step guide to do this.


 



* Source:  iFixit.com. Photo credit: Sam Goldheart and licensed under CC BY-NC-SA 3.0.

Remove the HDD and connect it to another Mac with a USB to SATA Adapter with Power.  The drives in the iMac are 3.5" so they need a 12V supply - more than what a USB port can provide by itself.  If you have a spare 3.5" drive enclosure, that will work as well.

Again, once connected, you can copy your files over from the drive to your connected computer.