My usb is not being recognized by horizon but my pc recognizes just fine.
-USB is formatted for my xbox
-I am running horizon as admin
Is your Xbox 360 on the latest dashboard update?
You might want to try a fresh install of Horizon from the link below after uninstalling your current version.
Download latest Horizon: https://www.horizonmb.com/client/v2/latest.php
Try a fresh install, and make sure your 360 is up to date on updates. Post back if you need more help.