This whole lot of stuff is taken from http://www.althack.com/, you can visit this website if you want still more infor or you run into troubles during the process. This is obviously how to boot from Pen Drive using Linux- DSL ie Damn Small Linux Distro.
Things Needed to Begin
Ø USB Storage Device - (256mb or larger recommended using USB 2.0)
Ø PC that can boot from a USB Device (check your BIOS or your User Manual)
Ø Syslinux 3.11
Ø HP USB Disk Storage Format Tool
Formatting The USB Storage Device
§ Insert your USB Storage Device into an empty USB slot on your PC
§ Download and Install the HP USB Disk Storage Format Tool. Once the usb disk storage format tool is installed, run it
§ Use the following settings in the HP USB Disk Storage Format Tool
§ Device: The name and capacity of your storage device
§ File system: FAT
§ Volume label: Name it what you want (I chose LINUX)
§ Confirm the Format by clicking Yes.
§ Once the Format is complete it will give you a list of information about the file system, volume, etc. about your device. Click OK.
§ Extracting Necessary Files
§ Download and Extract the Damn Small Linux distro (dsl-4.2.4-embedded.zip) to your USB device using Win-Zip or any extraction software.
§ Download and Extract all the files from syslinux-3.11 to a folder named Syslinux on your primary hard drive (mine is C:)
§ In Command Prompt type cd c:\syslinux\win32 (substitute c: for the drive letter of your hard drive) and Press Enter
§ Type syslinux.exe -f F: (F: reprents the drive letter of my USB Device. Yours may be different. GET THIS RIGHT). Press Enter.
§ Exit from Command Prompt
Booting to Linux
Keep your USB Device plugged in and Reboot your PC. Enter your BIOS setup (usually by pressing F2 or DEL) and set your Boot order to boot from the USB Device First. Exit your BIOS and Save the Changes. Since there are MANY different BIOS you must figure out on your own if your PC supports booting from USB.
Voilla it works fine for me, please search for requirements or softwares needed in Google and you must be enriched with the best one always.