[Incudie] tipped us off about a method to fix a borked HDD in your Xbox 360. Many of the one million consoles banned earlier in the month also had the hard disks scrambled making off-line gaming impossible as well. It turns out that this is caused by having a ban flag in the NAND chip on the motherboard. It has been discovered that because of wear levelling, the NAND will have two copies of the “secdata.bin” file which stores the ban flag. Please note, this will NOT allow the console to use Xbox Live, it just re-enables the HDD.
The quick and dirty of the fix is as follows: First the NAND is dumped from your Xbox 360 to a computer. After verifying the file, it can be opened in a HEX editor and the two copies of “secdata.bin” located. Once identified by date, the older version is injected on top of the newer to overwrite the ban flag.
Looks like this is not for the faint of heart, but if you got banned for modding in the first place this should be easy to pull off.
Update: Looks like xbox-scene now has a collection of apps to help you with this process. [Thanks CollinstheClown]