Take a deep breath! This is something that is easily handled-but it isn't obvious and that's what's been scaring you.
Turn off the computer. Now turn it back on, and as you hear the boot chime, hold down the "Alt/option" key. Hold it until you get a screen that shows two hard drives, labeled <your Mac hard drive name> and <Windows>. Use your mouse or cursor keys to select the Mac disk and your machine will boot into OS X. As a final step, go into the "Startup Disk" preference pane in System Preferences and make sure that OS X is selected as the default boot OS.
Now you can either use the Boot Camp Utility to get rid of your other partition, or go looking for a full version Windows disc.
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