after days of trying, i can't even test ubuntu from cd!

i'm trying 2 test drive ubuntu- so i downloaded the program, extracted it using "zipeg" and burned that all on a cd, but my pc won't start up with it. it's set so that it should start up through the disk drive, but it doesn't .
i'v read tons of advices from everyone (for others with similar problems) but nothing works, i tried the wubi or soemthing like that whihc is supposed 2 b like installing awindows program, but that doesn't work either... dunno why.
can anyone help me through this?
advice much appreciated.
tom.