Microsoft expects you to pay close to $200 to upgrade your Xbox 360's hard drive from 20GB to 120GB. That's about $150 more than a 120GB SATA drive actually costs. But with this slightly tricky hack, you can save a bundle while boosting your game console's storage capacity to hold more music, video, and other media files.
You'll need a DOS installation on a writable flash thumb drive for this hack. (The utility doesn't work under Windows, and you'll also be disconnecting your PC's hard drive.) First, grab a spare USB thumb drive and copy the HP Drive Key Boot Utility to it. The utility is designed for HP flash drives, but it works on other types of flash drives, too. Also download and mount a DOS image file.
This hack is designed to work with a specific drive, the 120GB Western Digital Scorpio, model number WDGWD1200BEVS. You'll be replacing the drive's native firmware with Xbox-recognized firmware. You can track down the firmware online by doing a search for "hddss.bin 120 Xbox 360." Place the hddss.bin file in the root of your DOS thumb drive.
Once you have these items and files ready, begin the upgrade by removing your Xbox 360's hard drive from the game console.
(For more hands-on hacks, see "Extend Your Wi-Fi Range With a Parabolic Reflector," "Add a Second Hard Drive to Your TiVo," and "5 Laptop Upgrades You Can Do Yourself.")