BigBodZod 2 Sie, 2013 - 11:52
Custom Display Resolution
Credit goes to Widescreen Gaming Forum:

Go to \base, and edit DoomConfig.cfg.

Find these lines:

seta r_customHeight "xxx"
seta r_customWidth "xxxx"

Change the x's to set your resolution. Now find this line:

seta r_mode "x"

Change the "x" to "-1".
Find this line:

seta r_aspectRatio "x"

If your screen aspect ratio is 16:9, change the "x" to "1".
If your screen aspect ratio is 16:10 or 15:9, change the "x" to "2".

As with any .ini solution, if you cannot find any of these lines in your DoomConfig.cfg file, just add them in manually.