Booting a computer from your USB flash drive may seem like a daunting task, but it is actually quite easy. With the right equipment and some basic knowledge, this very useful technique can be taken advantage of in all sorts of different circumstances.
The first thing you will need to do this is a compatible USB flash drive. Most drives are bootable but some are not, so it pays to ask before making a purchase or to do a bit of research online before picking your drive. This is not something the average salesperson will know nor do most companies make it clear on the packaging, so the internet is your best source here. Try to find a drive which has been used successfully in the past, like Corsair's Flash Voyager. The size of the drive is going to be an issue depending on your requirements. If you need to place an entire operating system on the drive, for example, you may need something a bit larger than what you have lying around.
The next step is to make sure that the motherboard which you are working with supports USB booting. To do this simply enter the BIOS (this can usually be done by press the Delete key while the computer is posting) and go into the menu selection titled something like, "Advanced Features". This process is a bit different for every BIOS so you may have to search a bit. Once here look for the boot devices, which will be placed in order: 1st, 2nd, 3rd, and so on. Normally the computer will attempt to boot from the CD-ROM or a specific hard drive first, but you want to change this to the USB drive. The proper selection to do this varies depending on your BIOS version but it be USB RMD-FDD, USB ZIP, USD HDD, USB CD-ROM, or something close to these. Once these is chosen as the 1st boot device you can move your hard drive and/or optical drive down the line (so they will be used if a USB device is not present) or remove everything (so that the computer will only boot from USB). A little trial and error may be needed here to make sure you have chosen the right boot device.
With the BIOS properly configured all that is left to be done is to save the settings and exit. A quick restart and you will be ready to boot from USB. Of course, this is supposing that your USB flash drive already contains the appropriate data.
This part is either very easy or a bit tricky depending on what you need to do. To properly format the USB flash drive you can either use a utility program or use a specialized tool within the software with which you will be booting. Many USB drives will include some sort of software utility which will allow you to format the drive and make it bootable. If your drive did not your drive did include any software HP has a program available which is quite popular. You can find it here. When formatting make sure to use the FAT file system.
If you looking into booting Linux from a USB flash drive there are a few different options, but I have had the highest success rate with Syslinux. This is a lighweight Linux bootloader mainly used for floppy media. This can be useful for distributions of Linux which are tough to get to boot from USB, but some do not need this. Puppy Linux is extremely easy to get to boot from USB and it actually has a built in tool for formatting a USB drive to do this. Other Linux distributions, like Feather Linux and even Fedora Core 3, have been known to work as well.
The quickest way to install Puppy Linux onto a USB drive is to first use it as a Live CD. With is running as a Live CD all you have to do is:
Setup > Install onto a USB stick > (Answer the questions)
After this is over your USB flash drive will be ready to boot Linux onto practically any system. Puppy Linux is the easiest, but the a similar process can be applied to many other distributions.
Booting from your USB stick is quite simple once you know the basics. When you want to start your computer in DOS mode at the A: prompt, boot into Linux, or something more complex, it just takes a little bit of hardware, a few programs, and some patience.