we have a video card for our pc to record our sons favourite programme, i occaisonally use it at weekends if i want to watch something but others dont, its very useful!
however, we have a pci video card which you have to install internally. if you get a usb card, which you just plug into the front or back when you need to, the picture quality is of less quality. if you get one decide if you are capable of installing new hardware (its no more difficult than installing new ram (which is easy)) as a pci video card is all you should really consider.
thankyou boobesque,i was thinking more on the lines of downloading one of these tv providers who charge 30 bucks ,if you search tv you will see what i mean