To boot linux from usb flash drive you need a USB Flash Drive around 2GB and you need to download some of the following Software.
1==>Download Universal USB Installer from here.
2==>Download a linux distro in this case i am using Kubuntu .
after that run the Universal USB Installer then it will ask you to agree the License Agreement click “a Agree” to agree the license agreement after that setup your slections page will appear
Then select your linux Distro that you have Downloaded e.g. “kubuntu”
Browse the linux distro that you have downloaded e.g.”kubuntu-11.10-desktop-i386″
Then Slect USB Drive the e.g.”H”
Then click “Create” to extract the content of the iso into the USB Flash Drive.
This process will take 4 or 5 minutes after that it will say completed “click cancel to close the window” then restart the computer “Rember to plug the USB Drive into the computer”
then a boot screen will show(if boot screen dosen’t show go to your bios and select boot option and change to usb first or you can go to boot option and select the USB Drive to boot )
Select Run linux to run the linux Operating System.
Know you run linux operating system from your USB Flash Drive .