First of all, I am shocked, as I have never seen Lubuntu on a CD. Didn't realize they had a version that small. Wondering what software it has on it.
Also, you said XP stopped booting, what did it do? (since Linux isn't booting either, wondering if you have a hardware failure).
I think most of us have done stupid things at one time or another, so you did remove the cd before rebooting so the hard drives would boot?
If so what does it do? (did it just show up as a command line, # )