I tried several and prefer WinDeu....once you get the hang of it, which
doesn't take long, it's a breeze. It is prone to occasional crashes
(rare but it does happen) so save and save often.

I personally prefer Doom Construction Kit (DCK), but haven't
been able to use it on my new machine, because the setup does
a crash-and-burn half way thru detecting the folders.

As for now, my wad editor of 2nd choice is WadAuthor.

If you attempt to construct fine-crafted level geometry, WinDeu32 is the
first choice. That's what I use.
It is a bit dated though and does lack modern features like support for
recent sourceports.

http://members.aol.com/jwjanko/windeu.htm

I installed Doom Builder as an addition, this is the standard editor for
Doom mappers today. Has everything, more or less, including an
OpenGL-preview window in which you can edit sectors and align textures.

http://www.codeimp.com/builder_download.php

With the upcoming release of Doom 3, it might be wise to include
something in the header about if you're doing editing for 1 and 2 or
3.

By the way, isn't it about time to update your OS?  But not to WinME.
Try 98se or xp.