What version of Vegas do you have and what have you tried?
See the screenshot linked below
This is what Id do navigating from the "media" option to the DVD, (although renaming them as mpg might help if they are on the HDD)
Once youve navigated to the DVDs
video ts folder, open it and where it says files of type:
choose All files, instead of the default
All media files, VOBS will become visible (and importable)
Just make sure it isnt from copy protected DVDs
http://farm4.static.flickr.com/3202/...bba43f88_o.jpg