First of all: your dosbox install folder(c:\dosbox\) and virtual C mount sux for Win7.
For the thousands time: while it was OK for XP to work as this, from Vista and certainly for Win7 it is WRONG.
Read and apply this:
http://www.dosgames.com/forum/viewtopic.php?t=13511
XP and Win9X times are gone, adapt yourself to a more secured OS.
W3D should be in c:\users\your name\oldgames\W3D\
\oldgames\ should be mounted as virtual C
Dosgames should NOT be buried in multiple level directories.
\dgames\w3d\ is not good.
Adapt yourself to a modern OS and correct your dosbox mounts.
Once done:
Game path in windows:
c:\users\your name\oldgames\w3d\
Path in dosbox:
c:\w3d\
Then the editor will find the needed files.
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[Optional
But I do NOT advise this]
You can eventually try to alter the ini line
"game_path=.c:\games\dgames\wolf3d"
should be
"game_path=.c:\dgames\wolf3d"
as c:\games\ is mounted as virtual C,
makes your WINDOWS path c:\games\dgames\wolf3d\
but makes your DOSBOX path
c:\dgames\wolf3d
Possible it will work that way, but nevertheless, your mounts are WRONG for Win7, Win7 is protective towards everything in C:, read/write access is unpredictable for programs and sooner or later you'll hit a wall, adapt yourself, even if you run as admin (something you should NOT do)