Hi, your hard-drive is not really built in. If you open up the right panel, you can swap out the hard-drive. Just letting ya know. But yea, I believe you can boot off linux in your external harddrive. I've never done that before so I can't tell you if that's possible or not but it should be possible. I have done dual-booting. It's simple, you have winxx running as your primary OS im assuming. Boot up your linux (whatever distro) and install it. Make sure it installs on the empty hard drive. Then you have a choice of your boot loader (lilo or Grub), either one is fine. After the install is complete and you reboot your system, your boot loader will load up and you will have a choice of choosing which OS you want to load up. Try that...