Deleting OneStep iDVD projects afterwards

[bigbusdriver]

Have used Onestep DVD to make three DVD's (using iDVD6 / Tiger) but have found a lot of disk space used up afterwards (not surprisingly). Help tells me to Choose Advanced > Delete Encoded Assets, but on selecting Advanced, find all fields light grey ie not selectable.

Any ideas please?

 

[NAG]

Probably related to all the dv files created in your movie folder.