I have ubuntu8 and ubuntu10 on my system, and want to also install windows 7. i have read that i need to first install windows and then ubuntu etc, but i currently have ubuntu first. once i install windows, i think it will mess up with grub. How will i access ubuntu after i install windows and fix everything that might be broken? and exactly what will be broken?
Windows will replace the grub bootloader with the ntldr bootloader, which doesn't understand linux. You'll need to re-install grub as your bootloader and configure it to see each OS. I would back up your grub config before-hand and then add Windows.
Well, actually I'd just run a VM under ubuntu... but up to you.