Installing and USB Boot problems

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http://askubuntu.com – I initially tried running Ubuntu off of a USB flash drive but the files got deleted, now when i boot my laptop it shows both Windows 7 and Ubuntu operating systems but the Ubuntu system says its missing a file and cant run it After the files where lost i downloaded Ubuntu on a CD and installed it into my hard drive following the instructions on the installation menu but the same error message shows up whenever i try to run Ubuntu. It says im missing some files, as if it were still trying to run it from a USB How can i remove the nonfunctional Ubuntu from my boot menu? (HowTos)