Ubuntu Linux is supposed to be a good "newbie" system, a couple of variations depending on the desktop used, Kubuntu-KDE, Ubuntu-Gnome desktop.
(Linux uses many different window manager systems, some heavy system users, some almost no memory footprint at all. Known as light footprint window managers. IceWM, Enlightenment, KDE, Gnome, all Linux window managers, that display your desktop and apps. MS uses 1, called explorer.exe.)
Linspire is good, but the one click app service costs.
Fedora Core is the community version of RedHat Enterprise system.
Mandriva Linux is the one I favour, in the 2006 distro, I haven't upgraded to 2007 yet. Easy configuration, plays nice with windows SMB over a network.
DeMuDi is for arty types, music and multi media specific.
Debian is the full on "hackers" distro, that is, the "ubergeeks" toy, not the criminal type hacker, but the genuine geek.
Always check the HCL, (hardware compatability list.) Linux may not drive the latest hardware, especially the winmodem, winprinter type things. It doesn't play nice with some Canon stuff, but, it loves HP stuff.
Google "distrowatch" mate, best bet I reckon, is to download a "live CD" version and test. There is no need to install a live CD. The OS boots and runs directly from the CD, never needs installing, and you can test as many "flavours" as you like, with out any actual system disruption. A 700 Meg CD carries up to 2.1 Gb of transparently compressed apps, that are uncompressed on the fly. Try that way first is my advice. You can't hurt your existing installation of Windows that way.
Shorty.

