How To Boot From A USB Flash Drive
For starters this is still a developing science and most people have had good luck with at least one of these methods. Note that flash drives are often also called thumb drives, keychain drives, pendrives, etc.
A FEW THINGS YOU NEED TO CONSIDER IN ADVANCE.
1. The PC has to support booting from a USB flash/pen/key drive. There may be anywhere from 0-3 items to change in the BIOS to make this possible assuming your BIOS supports it. Some older bios's may refer to your flash drive as a USB floppy or USB zip.
2. The USB flash drive must support booting from it in general.
3. The flash drive must contain the boot/system files.
4. The flash drive must have bootsector area. This is done with special utilities.
5. References to "A:" drive lines in the autoexec.bat and/or config.sys files you copy to the drive after you make it bootable may result in errors.
Method 1 - The fastest and easiest utility to create a bootable USB drive. Screenshot. Click HERE
Method 2 - Try these 2 USB Flash Drive Utilities by HP/Compaq. They work with Most other brands of flash drives as well.
hpflash2.zip HP USB Disk Storage Format Tool. Formerly called hpflash1.zip
HP Drive Key Boot Utility Version 7.41
For the downloads section I use nLite to make and create the image file as you can import the service packs and do some tweaking to the install files.
1. Install the HP USB Disk Storage Format Tool and run the program.
2. Select the Device and the File system from the drop down menus and click start.
3. Close the above program and install and run the HP Drive Key Boot Utility. Selecting the appropriate drive letter. Click Next.
4.Select the circle on the top that says create New or Replace Existing Configuration. Click Next.
5. Select the circle labeled Hard Drive. Click Next.
6. Select Create New Filesystem. Click Next.
7. Select the circle labeled HP Firmware Flash Package. Click Next.
Method 3 - Suggested by Kevin Ying: UNetbootin
Method 4 - Suggested by Shep................: WinToFlash
BareBones Boot Floppy And ISO
DOS 7.10 | Readme
Bootdisks - PC Support - Essential Utilities Bootdisk.Com