I'm using Lubuntu 11.10. That's great, but sometimes I miss Ubuntu's eye-candy. I can install Ubuntu 'as a layer' on Lubuntu, so I'll be able to choose the 'layer' in the login screen. But doing this will leave typical Ubuntu stuff on my Lubuntu install as well, which bothers me: I want to keep the Lubuntu install clean.
I've booted Ubuntu 11.10 from a live USB, and then tried to install it 'alongside' Lubuntu (so I could choose the right operating system in GRUB). But this option doesn't show up. I'm not an expert at using the advanced installing mode, but this could be the key to get this done.
So, my question is: How can I install Ubuntu alongside Lubuntu, without changing the Lubuntu setup?