can't use D_E3M3 from SERMUSIC.WAD in another wad

When I try to extract D_E3M3 from sermusic.wad and put it in another wad, it doesn't play and XWE says "unknown file format" when I click on it. Same thing in Slade. What is going on?

edit: ok, managed to put it in my wad by deleting everything else from sermusic.wad and merging it with my wad in XWE. I wonder why it hates being extracted so much.

Memfis said:

Same thing in Slade.

I'd dispute that. I just tried and D_E3M3 from sermusic.wad could be played back, copied to another archive, and extracted correctly with SLADE 3 without having to do any mumbo jumbo.

I'm probably the only loser who has problems like this. Happened before with some random graphic from 3hafinal.wad - http://www.doomworld.com/vb/doom-editing/63909-sttnum4-from-3hafinal-wad/