In "What's Behind The USB Drive Revolution", we began an exploration of the different types of compact, removable drives--sometimes called pen drives, thumb drives, jump drives, key chain drives, and so on--that attach to your PC via a USB port. Usually, these devices electronically disguise themselves so the PC they're attached to treats them as a kind of floppy drive, but they add vastly more storage than any floppy can. USB drives typically add anywhere from 16 Mbytes to more than 4 Gbytes of portable storage to your system.

Almost any USB-equipped PC can read and write files to these devices, making them a nearly universal tool for moving larger files around without a network, or even serving as a back-up medium for selected files. Most newer PCs also can boot directly from these devices, and that brings us to today's topic.

Simplicity Itself, Except When It Fails
In theory, making a USB drive bootable should be utterly simple: After all, a USB drive presents itself to the system as a kind of floppy-like medium, and every PC for the last 20 years has known how to boot from a floppy. But, naturally, it's often not that simple: There can be problems on both the software and hardware side of making a USB device bootable.

On the software side, there can be issues with finding the correct, essential boot files in the first place. Some operating systems--many Linux distributions, for example--lack a simple, obvious "make boot floppy" menu item; you may need to cobble together a boot floppy on your own, or download a preconfigured boot floppy image that may or may not contain the exact files you need and want.

Windows can have problems, too: For example, in newer versions of Windows, your main operating system may be New Technology File System (NTFS), but the operating system's "make boot/system floppy" function will produce a DOS-based boot disk that won't give you access to your NTFS files. And there can be other software problems, too.

On the hardware side, some older PCs simply cannot boot from any USB device. And other older PCs that can recognize and handle a version 1 or 1.1 USB boot device may choke with faster USB 2 bootable hardware.

So you see, booting from USB devices isn't quite the walk in the park that some vendors might want you to think!

BIOS Support
The most fundamental go/no-go factor in using a bootable USB device is in the system BIOS (Basic Input/Output System). Either it will support USB booting, or it won't. If it does support USB booting, you'll probably have to enable the function, but that's relatively easy to do.

First, check to see if your PC's BIOS supports USB booting at all: Do a full power-off restart of your system. As the PC wakes up, usually right after the first "all's well" system beep, watch for text messages that briefly appear on screen. (If your PC normally shows a logo or other graphic at boot, try hitting the ESC key to reveal the text messages that the logo normally obscures.)

Usually, the very first text message is from your PC's video system, announcing the make, type and version of the video card installed. But very soon after that, you'll see a message saying something like "Press DEL to enter SETUP." In some systems it's ESC, or a function key, or a key combination, instead of the DEL key; but virtually all systems announce some way to stop the boot process and enter the BIOS Setup program.