Horizon doesn’t seem to read the folder. Because when I input my hard drive the horizon doesn’t read it. Have done the “run as an admin”, done also uninstalling and installing, also done using different computers, also used modio. But nothing seem to read my hard drive. The only item in my hard drive is the “Content” and a not that has the name of the Harddrive on my xbox360. Is the new update related to it? 
:(:(:(:(:(
Please help me.
Is there anything in the Content folder?
Yes there are files. Actually there are 4 folders namely:
"0000000000000000"
"E00001B052D79751"
“E000002FD844B8FC”
“E00005DF52D79751”
The zero folder is for title updates and game settings and for music , vids. The E0000 folders are different game profiles one is your main while the other two are guests; and with in these are your game saves. The saves are sorted into folders by their game id number like 425307D5 for Fallout 3.
http://www.360-hq.com/xbox-tutorials-26.html for more info
another tool i would try is Xplorer360
What is that? Does it work like Horizon? And can it put downloaded dlcs to the hard drive?
Horizon only handles signed packages so if you are trying to put DLC on your flashdrive then I would go with FATXplorer. It was created by one of the beta testers here and is the best device explorer I have used.
Can you give me a link?
Thanks. I’ll try it
There are two types of it. What should I download? The 64bit or 32bit version?
Nevermind, I already knew. Thanks a lot to all that helped me, I’ll try all your options. Thank you. God Bless You!