XpressLinux is based on Kubuntu but has some nice additions for better Windows integration. It might be the perfect distro for a die-hard Windows user who wants to try Linux or have a dual-boot system:

From http://www.xpresslinux.com/about/:

XPressLinux is designed to be easy to use and familiar for Windows users. It will install easily over an existing Windows system, allowing the user to access their existing programs & documents.

Major features of XPressLinux:

• XPressLinux is based on Kubuntu and uses the KDE desktop.
• WINE is pre-installed, so you can run many Windows applications.
• VLC Media Player lets you play most common audio and video files.
• Firefox is the default web browser, for maximum compatibility.
• Your Windows drive is automatically mounted and the WINE file manager provides a familiar desktop.