Can any cards record direct to AVI ?

[picomode]

Why do all the TV cards record in MPG format ?
What format do the digital cards record to natively ?

Lastly, what do I need to get to use a digital card. Do the cable companies block digital if you don't get the set top box ?

[stustunz]

analog cards normally have mpeg encoder
digital card just save the stream which is decided by the broadcaster

where in the world are you its different depending on the country

[martint123]

Why do all the TV cards record in MPG format?

It is an industry standard and closely defined, chips are available. AVI could be almost anything internally.

What format do the digital cards record to natively ?

Whatever the broadcaster sends, they just (almost) dump from tuner to disk.