Shoutbox

I have just today bought a tv tuner card for my laptop. It is made by AVerMedia and supports HDTV as well. I have been fiddling with it and have got my tv stations programmed in and it works great and im really happy with the picture quality etc (especially on HD channels). However i just tried recording some tv to see how easy it was and recorded a minute of digital tv. I then went to where it saved and the filesize is ~70mb for one minute of video. It is set to record as MPEG II and for digital there is no other option besides record audio only (for analog tv there is avi, mpeg I, DVD etc).
So my question is surely there is a way of reducing the filesize. I see many capped high definition tv shows for download on the internet and a 1hr episode is around 350mb yet at the moment if i was to record a one hour episode it would create a file around 4200mb. Which is definately going to fill my harddrive pretty quick no matter which one i put it on. I bought this thing as a replacement to my crappy old vcr recording but am questioning its usability.
Can anyone who has used one of these type of things before offer any advice on operating it better and maybe adjusting some settings?
Thanks