I've been using Mepis on a second HD and I've had people over who nothing about computers and they feel just as comfortable with Mepis as WinXP. In fact the file system in KDE is easier than windows. I think Mepis is the best overall. Try it see... http://www.mepis.org

But do like Knoppix and Kanotix for live CD use! I just think Mepis has a easier wizard for HD install.