Digital Video + Storage space required

Can anyone tell me how to figure out how many MB or GB are required to store eg 1 hour of digital video?

A friend wishes to buy a laptop, video camera etc but first needs to figure out whether the laptop will handle what he requires. He intends to use the laptop to edit down about 20 hours of video into a one hour presentation, shown using powerpoint on the laptop.

Also interested to hear any suggestions on how to archive video, in such a way that it is easily retrievable.
Thanks for your help.