HELP RECORDING DVDs over 2hours

Here's my problem.  I have a sony DVD burner. It plays and burns dvd and cds.  I can get it to burn dvd but can't burn dvd movies over 2 hours.  (I do my burning using Windows media player.)  I went and bought a dual layer pack of blank dvds because the sales guy says that dual layer dvds have twice as much storage.  I have a dual layer dvd burner 16x came with Nero software. 

 

When I try to burn Pulp Fiction (159 minutes).  There is a message that says "Will not fit"  on the 240 minute dual layer dvd.  Other movies on burn list say "May not Fit".  What do I need to do to solve this problem?  Thanks for any responses.