Because some of the other half is taken up with Windows OS and a host of other stuff.
I have heard, but do not know if true, that it is possible to tweak the program settings in the box to gain access to something like 40GB extra as this is unused. Like I said, I do not know how credible this is, but as there are RS232 ports on the rear of the sky boxes, it is possible to connect them to a computer so it may be possible to do.
What channel do you watch then bob? Besides the BBC, which channels DONT show adverts every 5 minutes? Perhaps theres a channel I havent heard of on cable TV which is advert free? As it is, we are in a minority to whom cable TV is not available. Sky+ at least provides more opportunity to get around the adverts
Thats what pees me off weather its cable/sky etc.. adverts some programs are on for 5mins or so then there's an ad. And when the programs near the end they have an ad