DOOM Builder opening Legacy maps in other mode

I was trying to open up some of my old Legacy maps I'm working on, under DOOM Builder under DOOM/HEXEN format, but alas it won't budge. Is this even possible?

... Doom Legacy format don't is a correct ?

2 choices:

1) Try converting it to Hexen format using Zwadconv, a utility which can be downloaded from the zdoom site:

http://zdoom.org/download.html

2)If that fails, and gives you something totally screwed up (which is possible), then your only other choice is to copy and paste your current Doom format map into a new Doom in Hexen format map. Keep in mind you can only do this with the sectors, lindefs and sidedefs. Things, actions, etc can't be copied over since they're all different numbers.

I'll give the tool a shot, as COPY & PASTE totally fucks up what I've got going...

...it's a tricky one.