Ok, I finally got DB to find the configurations
Only by running directly from the Program Files/Doombuilder directory could I get this to work
Now, when I try and set the IWAD using Tools>Configuration, it works for a bit, but
When I try and make a new map, it says "Could not find Playpal"
The next thing I did was to insert a sector, the floor and ceiling textures both said "flat not found". I tried to check this out, and it crashed.
I was using Chex3.wad as the IWAD, does this make any difference?