I also have a Packard Bell laptop (but mine is an EasyNote 2004 model) running Windows 7.
Most older laptops need a fresh reboot in order for them to find the TV screen through the VGA port. The fact that you say it works sometimes and not others might be a motherboard issue; some people flash the BIOS but I highly recommend not doing so.
I'd suggest taking out the RAM and the CMOS battery for at least five minutes, then doing a fresh boot. When the Packard Bell picture is supposed to pop up, that's when the TV should display your Windows startup screen. If that doesn't work try it on another TV; if that doesn't work all I can suggest is replacing the VGA port - or to save time and trouble get a newer laptop.