From what you said initially, you want the TV as a secondary monitor.
If you want two monitors then you need two outputs from your PC video card.
As your TV/monitor has an HDMI input then feeding it from a vga output on a video card will not make best use of the quality available on your TV.
So I suggest that you buy a video card that has both hdmi and whatever your current monitor requires (presumably vga).
Some cards have vga + DVI + hdmi, so you would be ready to upgrade your vga monitor to a DVI connected LCD monitor in the future.
As before: make sure that the card you buy matches what your motherboard supports, e.g. AGP, PCI express.