Xbox 360 system update failed, error code: 4099-43C5-B800-0F00-C000-0013
If you are having this problem on your xbox 360(even if it’s not exactly same code, but the message is the same, here is the solution.
First you have to identify xbox 360 update that caused this problem so that you can fix it.
To do that you need to convert this second hex number sequence(in my case it is “43C5” to decimal first).
There are many hex to decimal number converters online, here is one: hex to decimal converter
When you open that site you enter your hex number(like I said in my case it’s 43C5 if your isn’t the same, you just enter that second number sequence of your error code)
in column “Enter hex number:” and press button “convert”, and you get your Dashboard number(in my case I got 17349), so if you are having that Dashboard here is the link so you can download it:
If you don’t have same dashboard number, just google your decimal code that you got and add dashboard and you will find it easily.
After you download correct version, unzip it and copy your “$SystemUpdate” folder to the root of your USB flash drive(make sure it’s FAT32 formated first)
After that, plug in your usb flash drive in your console and just turn it on and follow instructions on screen.