As it looks like you are in Australia, if you have DVB-T digital
terrestrial TV in your area you should get a digital card. Getting a dual
tuner card allows you to watch another channel while recording another, or
recording two channels at the same time.
There is a PCIe Terratec dual tuner digital card, that was first to
market, but I have heard that tuner sensitivity isn't that great and I
don't think it has Vista drivers yet.
The Hauppauge Nova-T twin tuner version PCI card is supposed to be good,
and has Vista drivers by now, I think.
I am not sure if you can get this is Australia, but this is the best card
you can get and I have one myself - Black Gold PCIe dual tuner
digital/analogue hybrid. It has two digital tuners and two analogue
tuners, in case you move to an area with no digital coverage. The picture
is excellent, but there is no included remote, so you need to get a
Microsoft MCE remote control.
http://www.blackgold.tv/
http://www.gta-ltd.co.uk/TV_PCIe_Dual_Cards.html
ss.