[ubuntu] unable to log on pc PLEASE HELP

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http://ubuntuforums.org – Hi I recently had Ubuntu on a partition, but it didn't work out so I went on windows 8 partition and deleted that partition. However, now when I restart my computer it will not load anything and gives an error of Error: unknown filesystem. grub rescue> I don't know what to do and I don't know how I can log back into windows or anything. I download an ios of ubuntu and simply put it on a CD to load. I can't use the click f12 to boot either, it seems to not work. all the help is appreciated thank you. I really need this computer working again thanks (Hardware)