Here is a short guide on how to make a bootable Ubuntu USB flash drive. I will show you how to format your usb flash drive and create a bootable flash drive using the Startup Disk Creator and a Ubuntu 11.04 “Natty Narwhal” Alpha 3 iso image. Before you start you need to download a Ubuntu iso image, you can download Ubuntu 10.10 “Maverick Meerkat” from this page. Or you can download the Ubuntu 11.04 “Natty Narwhal Alpha 3 from this page.
To make the bootable usb flash drive start the Startup Disk Creator (System -> Administration -> Startup Disk Creator) and load the Ubuntu iso image. To do this click on the Other button and go to the location where you saved the download iso (i saved my iso on my desktop). When the image is loaded insert your usb flash drive into your usb port. When inserted it will appear in the Device section. Select the device by clicking on it and format the device by clicking on the Erase Disk button. Before the usb flash drive is formated you will be asked if you are sure about erasing the disk.. click on the Yes button. When the disk is erased a window will popup showing you the content of the empty disk. Close the window and select the newly created partition by clicking on it. Now click on the Make Startup Disk button and wait until Startup Disk Creator is finished making the bootable usb flash drive. When Startup Disk Creator is finished click on the Quit button and open your usb flash drive (Places -> YourUSBFlashDrive) to see if the files are on it. After the check you can unmount your usb flash drive and you are done and now have a bootable Ubuntu usb flash drive!!