[ubuntu] operating system not found - wipe disk?

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http://ubuntuforums.org – Hello, I'm a complete newbie and this might be a very silly question, but I'll ask anyway as it would be a catastrophe if I mess it up. I installed the Oracle Virtual Box (didn't realize until now Ubuntu had its own version) and then proceeded to install Ubuntu 2.04.1 Things had gone pretty smoothly in the early going and I was following along in the VB Manual until I came to a screen that scares me: I'm pretty sure that just means there's no operating system in the disk/partion/container just created, but want to make sure I don't format my whole hard drive or something. Thank you for a (Hardware)