I downloaded Ubuntu 12.04, then using the tool Startup Disk Creator i made the live usb. I checked that it's bootable
Device Boot Start End Blocks Id System
/dev/sdb1 * 62 15635593 7817766 c W95 FAT32 (LBA)
Now on my lap top it boots nicely, but on two other machines that don't have any installation of ubuntu(no Grub) it doesn't boot.
I changed the booting order so that USB is before HDD.
So i think i did everything i know, but no luck. How can i use this USB drive on other devices that don't have any previous ubuntu installation.