Ubuntu comes on a "Desktop CD". This is a disc that you can boot from, try out Ubuntu directly from the CD, and if you find that everything works correctly you can run the Installer program. Unless you double-click the "Install" icon on the desktop, your hard disk will not be touched.

Give that a whirl to see if your hardware is supported. There is the possibility that you can get your wireless working even if it doesn't work out-of-the-box on the Desktop CD. Note that 3D acceleration will not work out-of-the-box, but the proprietry drivers for ATI or Nvidia can be loaded in once Ubuntu is installed onto your hard drive.

Also, you might not know this already, but it's a simple affair to install Ubuntu alongside Windows, so each time you turn on the computer you can choose which one to load. Defragment the hard drive from within Windows, run the installer from the Desktop CD, choose "Resize an existing partition" when prompted and Ubuntu will do the rest.