Downloading from the disk
So I have a disk copy of Battlefield 3 but every time I go to install, its downloads from Origin. I have a very slow connection which would take me a day or better to download. Is there anyway to install from the disk I bought?
You should definitely be able to install from the disc via an autoplay option that should open when you insert the game into your computer. If the autoplay option isn't working, first make sure the disc is in your system, then open "My Computer" from the start menu or desktop. Once there, you should see the BF3 icon loaded onto your disc drive. Click on the icon and this should launch the auto installer, or right click "Explore," and find the installer on the disc yourself.
What Origin is most likely downloading is the latest Title Update for BF3, which I believe is quite massive. You will need this tilte update to play BF3 online, so unfortunately, with your slow connection, it might take awhile to start playing even if you successfully install the game itself from the disc.
Let me know how it goes.