you could download a copy at ubuntu.org. what you will get is an .iso which you have to burn to a cd. upon starting the computer, insert the disk and select the boot option of booting from a cd/dvd. there will be a menu giving you options. the first one will make you "try" out ubuntu and the 2nd option will install ubuntu to your harddrive. be noted that you can also dual boot via autorun(if disk is inserted while windows is running) and selecting the 2nd option. this option will give you the chance of trying out ubuntu while installed in the disk and having the option to go back to windows anytime you want and uninstall it like any program.

but tell you what, you can use windows programs using WINE or even virtualbox/virtualmachine. you have more eyecandy than mac and vista combined for the performance of a win98 on an uber PC. which is crazy

if you can't figure out how to burn .iso, you could drop by my condo and i will issue you a copy