To uncripple your HDD after being banned from Live you need to build a simple NAND Reader/Programmer. You will need some resistors and a diod plus 25-Pin male LPT connector. You can use the following diagram to build your LPT programmer (pay attention to the SPI part and leave JTAG part alone).
After you have built your LPT programmer and soldered wires to your XBOX Mainboard, now it is time to Read your NAND. In order to do so, you have to download NandPro program from usual places. When you have downloaded the program, open it's folder and run 'port95nt.exe' to install the DlPortio driver. Then open a windows command prompt (CMD) and navigate to NandPro folder and use the following command to read your NAND file (You need to have your power cord connected to your console but you shouldn't turn on your console):
nandpro lpt: -r16 nand.bin
For a 16 MB NAND it may take about 45 Minutes to read it completely. After you have read your NAND for once you need to read it again (save to a new file), in order to be able to compare two files so you can be sure that you have read NAND correctly!
Compare two files with a Hex Editor (like WinHEX) and if both files are the same, then you can go on with the rest of the tutorial, but if there are some differences then you need to read it once more and compare again. Just make sure that you have the correct dump before you proceed to edit anything in NAND file and rewrite it! (Or you may lose your console!)
After reading and comparing and when you are sure that you have the correct file, its time to solve the game installtion problem.
Now you have to download FindSecData v0.6, again you can find it on the Internet with a simple search in Google.
After you have downloaded the program you need to use it as the following: findsecdata nand.bin
Program searches for previous versions of secdata.bin in your NAND file and at the end it gives you something like this:
nandpro.exe lpt: -W16 secdata00DB.bin 0E3 1
nandpro.exe lpt: -w16 Patchedfiletable00E4By00DC.bin 0E4 1
Of course the values will be different for you but you should use the exact letter case for 'W' because it makes difference! Now use given commands to write patched files to your NAND. After writing those two blocks you can assemble back your console and test it by trying to install a game on your HDD.