ah, if you really want to get a proper feel for ubuntu witout installing it you really need to make a persistant 'pendrive'
ie, put it on a USB stick with read AND write capabilities, otherwise it wont be able to run the upgrades for drivers you need when you have/add new hardware,
remember, on a DVD it only has your ram to work in, dunno how much ram you have, but do you think windoze could run in 1Gig? Ubuntu can , albeit slowly, ideally it needs about 6G min to put all its files and system on,
but, it can run on just under 4G happily enough if you dont add too much stuff on.