HI Martin

I have a follow-up question.  When I load the default protocol for the NRRD DWI's
I get the following message:
The following programs have not been found.
Please enter the path manually if necessary:
> bet2
> DiffusionWeightedVolumeMasking

Is it necessary to have the nodif_mask for running DTIPrep successfully? 
I ask because I already have made masks using bet2, and for some reason I can't find the path to Slicer's DiffusionWeightedVolumeMasking

Cheers
James