I have to purchase a digital game i should already have?

Make sure you're signed into the account that purchased the game. You can also verify if you did purchase it (or redeem a code for it) on your account at http://account.microsoft.com

If you're 100% sure you're using the account that purchase it and it's not showing up, you'll need to contact support. http://support.xbox.com/contact-us

Hey there Raphael! I'm still seeing Dead Rising on the US Marketplace (LINK) so I don't believe it was taken down. Can you confirm for
us if you have indeed switched consoles at any point since purchasing the content. Also, have you changed your physical location and/or your account region since purchasing?

As for downloading issues themselves, our best suggestions are to delete, clear cache, and download again. You can also try removing your current storage device and download the game to another one. Let us know if that helps, thanks!

Thanks for the help Judge Bergan, but unfortunatelly it didn't solve my problem. I have already contacted microsoft support, spent hours on it, and did all the troubleshouting, including transfering my content licenses. After some online research, I strongly
believe the game was removed from xbox live download servers or something, as other users are having the same problem to even download the demo.

If it is showing as incomplete then the download is infact not completing 100%. Delete the bad copy of the download and keep reattempting to download the game. Since buying the game have you switched Xbox's? If so, did you ever transfer your content licenses?
Let us know.

I'm assuming you have already purchased it digitally to be asking this question and if that's the case go to my games on your xbox and it should be displayed with all your other purchases games.