If you want to flash the disc drive on your XBox 360, you are going to need to know the key to that drive or another one so that you can reassign a key to the drive after you flash it. This video will show you how to do that, as well as how to make your own DIY XBox connectivity kit. That will save you about $30 and make you feel much more legit as you hack away at you XBox 360.
Detailed written tutorial here.
From the creator:
To make it super clear these are the steps involved:
0. make a DIY tool to dump the key (or buy a CK3 etc..)
1. prepare your drive, the tray must be half open, SATA cable connected to your pc and rs232 adapter in place
2. dump key.bin , Identify.bin and inquiry.bin and create a dummy.bin file
3. patch ix15-liteon.bin with your dummy.bin to create your CFW.bin
4. erase your drive (only do this if you are sure you have the correct key extracted )
5. reboot the drive and flash it with your CFW.bin
6. if all goes well, go play some backups !