Delete original partition?

I have used bootcamp to create a windows partition and now find myself wishing to run windows exclusively. (heresy, I know)

I would really love to be able to erase my original drive and give the windows partition the extra space. Part of me thinks this is impossible but I figure I'll ask anyway. I get an error in disk utility saying i can't erase it because it is my startup disk, but when i change my startup disk in preferences, I still can't erase it.

If I can't do this I'll just have to erase everything and install windows, so no worries.