[ubuntu] Need help with dualboot

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http://ubuntuforums.org – I have two hard drives both of 500GB. I have windows 7 on it and the other one has two partitions one with 450gb and the other with 50gb. On the 50gb I installed the consumer preview of windows 8. I want to get rid of Windows 8 and install Ubuntu there instead. For some reason windows 7 won't let me format that partition and when I try to install Ubuntu it wants to delete both the 450 partition and 50 partition and merge it into a 500. I tried using the manual partitioning tool, but I kept getting a no root file system is defined message. I would greatly appreciated if someone could help me o (Hardware)