The Canon 5D needs ACR 3.3. A fresh installation of PS will have a lower version. You can confirm this by looking in PS Help > About Plug-in...
You must download the latest 3.x version and install it exactly following the instructions.
This didn't work because it seems that there isn't ANY version of camera raw installed in the first place, even when I install it exactly as the read me file specifies. It still tells me photoshop does not recognize the file type.
I'm worried if I uninstall and reinstall, I will mess up teh activation.
So, once again, PLEASE help.
After you have attempted your install of the Camera RAW update, what version of Camera RAW do you have installed? Use Help / About Plugin... / Camera RAW
Make sure there is only one listed, as well.
The last thing you need to do to sort this out is to uninstall/re-install. It wouldn't help anyway! Try what SS said and report back.