Remember that the 50 GB is just to store the raw footage.
You'll also need space for things like graphics, music, pre-rendered segments and temp files as well as the finished project, all of which will add substantially to the total.
If you want to burn a DVD afterwards, add even more space.
Swede, if possible, it's better to have a seprate drive your video/audio. It's faster if your OS/programs are on a one drive and your media are on another.