Kubuntu, Ubuntu, Opensuse. Just grab the Live CDs/DVDs and see which one suits your needs best.

Each of theses distros provides very good hardware support. Kubuntu/Ubuntu 9.04 maybe a bit better than Opensuse 11.1 due to the more recent kernel. Should run on just about any machine. Even if it's from Dell.

Both, (K)Ubuntu and Opensuse have a very big and active community. So if you face any issues with these distros, it's usually quite easy to find help and a solution.

If you are coming from XP/Vista, you'll probably feel more at home with KDE desktop environment (Kubuntu, Opensuse), than with Gnome (Ubuntu). Though i'ts certainly worth giving Gnome also a try.