Burning from Authoring program probs!

[Shocker]

Hi Im new to re-authoring,here is the situation.Using Powerproducer Gold I have uploaded a dvd that I created from Vob files.I can insert menus etc but when it comes to burning onto a new disc it states I havent enough space on disc!!
They came off a disc so why wont they go back to one? As I said Im new to the program,normally just convert to Vob and burn,but wanted to be more creative.

Edit: Also If I open vob files(one complete film or TV show)it seperates it into chapters in stead of just a single chapter.Each VTS file having a chapter.Why?

Thanks

[Shocker]

oops my bad! Realised my error now.