i have vista on my dell latitude D260. i wanted to 'upgrade' to ubuntu , so i downloaded and burnt the image onto a cd . when i try to boot via the cd nothing ever happens. in this lappie , when i go to bios tit asks me to give preferences to the booting order so i gave 1 to the CD and unchecked the others but when it statrs again the it doesnt recognise the cd and refuses to boot from it . what can i do?