ERROR!

I have used Legacy in the past with no troubles. What is "RUN TIME"? Also, while in console for Doom.wad, I attempted to ADDFILE P.WAD I have in the directory, console confirmed the load of M1-M9, showed the lump load of 100, but when warping to map for Pwad it crashes stating "cannot find flat 19". Can you tell me anything to try? Thanx

Sounds like Legacy has crashed, hence the "run time error" you've been getting. Could be any of a million causes for that, but I hazard it's a memory-handling or driver problem. The "cannot find [some texture]" error means your level uses an unknown wall/floor/ceiling graphic. Check if you have loaded all WADs necessary to play that level.