[ubuntu] Updating windows

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http://ubuntuforums.org – I've decided that I'll be updating to Windows 7 (a bit late, I know)on my machine. I dualboot with grub Ubuntu 12.04 and I will be doing a clean install. My plan was to backup all my files in the Ubuntu partition, but will completely erasing the C partition and installing a fresh new windows mess with grub or my Ubuntu partition? Thanks, any help is appreciated. (Hardware)