live usb flash drive

I recently purchased a flash drive with ubuntu 11.04 on it from ebay. When i received it i was very excited to use it i went to my brothers house and booted it from his laptop no problems. It was a toshiba satellite i dont remember which model it was running windows vista and i think it had about 2gbs of ram. So i go to school the next day and try to boot it from a desktop there it ran exactly as it did asking me weather i wanna install or run live i picked run live on the it did the same thing as it did on the satellite except when the ubuntu loading screen came up instead of going to the desktop GNOME/unity it went to a text based shell and said something about it not being able to mount /root or something i didnt write it down because i didnt have time. but it does that on every computer now. Now know i could just wipe the flash drive in put ubuntu on their myself but i would really rather learn more in depth with linux so i figured this would be a good opportunity ! so any help is appreciated.

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