HP nx6110

hi i have a HP NX6110, and i want to watch it on my tv, i got the lead (15 pins) that connect my tv to computer, when i connect them up the HP doesnt work, just says no signel, when i go in to my dispaly setting the only thing i can get on the tv is my background pic, no desktop or any thing, when i connect my dell up, it works perfect, any one got any ideas