[all variants] What is the proper way to triple boot

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http://ubuntuforums.org – Hello folks, I am currently triple booting Win Vista/Xubuntu 11.10/Linux Mint 15. Since I had been unable to update my Linux distros since Xubuntu 11.10 due to kernel problems with my laptop I had not bothered with this but now that I can I would like to update both my distros. The problem I have is that every time I install one distro, the grub2 from that distro takes over and breaks the boot splash screen from the other distro. So right now I have the grub2 from Linux Mint 15 and Linux Mint 15 splash screen come up on boot nicely, but now my Xubuntu 11.10 splash screen is broken I no longer (Hardware)