so... If I only have the one vga plug on the back of the tower then the answer is no?
and for the next question, how come when I plug the hdtv into the vga port I get no picture from the tower ( cant see anything)
exactly. if you have a single VGA connector you wont be able to use one than one screen even though the chip can theoretically handle it.
the g33 chipset is not made to push HDTV screen res and you will find even something as simple as a hd youtube video might be too much for it to handle.
the next question is hard to answer with out background knowledge of your hole setup.
it might be the TV needs to be told to listen to the VGA port to get the signal,
it might also be the resolution coming over the VGA port is not compatible with what the TV can show, think screen resolution, refresh rate.
the most hassle free solution (if you have a budget) $30 will get you a 8400gt from newegg with a HDMI port. not only that but it will be much better suited to processing HD signals and will let you run more than a single screen.