so if I install a PC Terrestrial tuner plus better video graphics card use my terrestrial aerial I could get Freeview HD????
I would suggest a video card with HDMI output.
According to Nvidia's website the card you have is entry level.
Something like 128bit with 1gb mem would be a vast improvement.
I upgraded to a Nvidia Geforce GTS450 which works well but unfortunately I need to upgrade my Monitor (1680 x 1050) to 1920 x 1080 one now to reap the benefit. The TV is a long way away from the PC (about 15m) and downstairs.