Hi guys,
I have a dv9088ea pavilion model with NVIDIA Geforce Go 7600. After a lot of testing on both windows XP and windows vista I have come to the simple conclusion that tv-out through an s-video to RCA cable (thats the standard red,white and yellow cable that are available on most TVs) does NOT work on our laptop models (and my guess is probably on any laptop using geforce go 7600). However if you try connecting your laptop to the tv using an s-video to s-video cable it does work!
I know most people are using older televisions that don't have an s-video port.. What I did was get a SCART with an s-video input on it. So you would connect your s-video cable to the scart and to your laptop and then put the scart in your tv. The laptop finally detects the external display and by pressing fn + F4 on the keyboard you can switch between displays.
Have in mind that I know that this solved me and my friend's problem, however we both have the specific HP Pavilion model dv9088ea. I have no idea if this solution will do for other models but you can try it out and see how it goes.
As a sidenote - HP customer service is appalling. I spent hours on the phone with them about this problem and have also exchanged many e-mails with them. They have no idea that the tv-out simply doesn't work with a standard s-video to RCA cable as it should. They told me to send it in but as you all know whatever problem you send your laptop to them with they will format the damn thing without thinking twice and return it in a couple of weeks! As if anybody can afford to go through that process!