Enable USB Boot Support
Most computers shipped within the last couple of years will support booting from a USB device. That said, this isn't always enabled by default, and it isn't always enabled for all USB ports on the system.
One of the first places to look for information about USB boot support, apart from the manufacturer's own specifications, is the system BIOS. In my own Dell XPS, for instance, the default USB handling option is to enable booting from attached USB devices -- but I need to press F12 at boot time to select something other than the default boot device, normally the hard drive.
Another important thing is that some of the USB ports in the XPS can be manually disabled from being polled for boot devices. This is done so that you can attach an external USB drive (whether flash or an actual hard drive), and leave it attached between reboots without worrying about it hijacking the computer's boot sequence.
The folks at the PenDriveLinux Web site -- a fantastic resource for all things related to running Linux on USB -- have a quick way to test USB boot support on a given USB drive and computer. They use the SysLinux utility to make the drive bootable and add a copy of Memtest86+ a quick way to see if boot support works. Note that if you're doing this on Vista, open an admin command prompt to run the makeboot.bat file or it won't work.
SysLinux is used widely to make flash drives bootable for Linux distributions, so it's a tool that we'll be coming back to. Note that if you get a "boot error" or other error message when you try to boot a drive processed with SysLinux, you may need to run the DISKPART CLEAN command on the disk (again, from an admin command line) to remove any previous master boot record information, reformat the drive, and then try again.
so this mean that i need to change some setting into its bio for me to able to boot this thing with ubuntu? i will check that site thanks for your help