ubuntu issue

alright, so i got an extra PC sittin around , and i figured hell, i'll install ubuntu on it. so im installnig it on a blank HD, and after it promtps me to restart the comp so it will finish instalation, nothin happens. what do i do? it jsut keeps telling me disk boot error, enter system disk and press enter, which does nothing.

also, i cant get the cd to boot up in my mac. im tired of mac-bloat-ware, so i figured id try that. i also held down C to boot from the disk as i started up, but no luck. how do i get it to work on the mac? >_> lol.