If a .mp3 has a .wma file format, mIRC won't play the file even though windows media player will.

Huh? mp3 and wma are different formats completely.

Edit: If you mean a renamed file extension, I'm just now listening to a .mp3 file renamed to .wma.. works fine.

A .wma renamed to a .mp3 plays fine in media player, but /splay gives an unable to play file error.

edit: I'm guessing mirc does internal error checking for files, but considering the player object does error checking itself, mirc doesn't need to.

Ah OK. When I tried that
1. Media Player did open it, but only after complaining about "the file has an extension that does not match the format...."
2. mIRC took a couple of seconds to throw the error. Perhaps without being able to answer the question above mci is returning the error and not mIRC itself.

Yeah, it did that.

Dunno if this is relevant or not, but all 5 files were copied from a cd onto the computer, and it does play 1 out of the 5 files.
It doesn't play renamed files that weren't from a cd either though.

Windows media Player looks at file headers and stuff: converts it to a tmp file if the headers do not match the proper file ext, and plays the tmp file.

eg....
>Trying to rename "Aphex Twin - Popcorn(Techno Remix).mp3" to "Aphex Twin - Popcorn(Techno Remix).wma" ends up with WMP doing...
>>Copying "Aphex Twin - Popcorn(Techno Remix).wma" to your temp folder, and renaming the file to "Aphex Twin - Popcorn(Techno Remix).mp3"