I ran Suse for several weeks and wiped it out.
I tried CentOS and PCLinuxOS using an old graphics card (with my built-in
graphics card it is impossible):
sites.google.com/.../adsl-pppoe-configuration-und\
er-various-linux-distributions

and an older version of Knoppix:
sites.google.com/.../snapshots-of-knoppix-li\
nux-on-my-pc

As alternatives to Ubuntu on desktops I would recommend Mepis, Antix Mepis,
CentOS, Debian, PCLinuxOS, Dreamlinux (I used it but wiped it out), Fedora or
even Knoppix or Kanotix.
For very convinced Windows users I would recommend Slax, NimbleX, Knoppix,
Puppy or a puplet and Damn Small Linux.