I made this alias for a friend since for some strange reason he uses WMP, lol.

Prerequisites:
This requires a plugin for WMP to write the now playing info to a file.
The website appears to be long dead so here is a download link. http://www.mediafire.com/download.php?ojbr7qatyh83txd

Close WMP, install the plugin, open WMP, a dialog should appear for the plugin options. Either change or leave the file path for the output file. Leave the text for "no media played" alone and replace the attribute text with Author|Title|Duration|FileSize|FileType
Then hit ok, play something, and find the output file inside the WMP directory or where you changed it to (file path for myself shown below)
C:\Program Files (x86)\Windows Media Player\playinfo.txt

After you have the WMP plugin creating the now playing info text file, it's time to load the mirc alias up.

Either load into the scripts editor aliases tab or place inside a file and add alias before each alias name and load the file.
Then change the path to the now playing text file and save. Then you'll be good to go.

Credits:
The now playing WMP plugin is copyright Cina.com 2003.
The gettokn alias is from someone on the mirc.com forums.

wmp {
  set -l %info $read("C:\Program Files (x86)\Windows Media Player\playinfo.txt",n)
  msg $active 3¥4WMP Now Playing3¥ $iif(%info == no media played,Nothing playing,$iif($gettokn(%info,1,124),7Artist:11 $v1) $iif($gettokn(%info,2,124),7Title:15 $v1)  7Length:11 $duration($gettokn(%info,3,124),3) 7Size:11 $bytes($gettokn(%info,4,124),m) $+ MB 7File Type:11 $gettokn(%info,5,124))
}

gettokn { set -l %c \x $+ $base($3,10,16,2) | return $remove($gettok($regsubex($1,/(?<=^| %c )(?=$| %c )/gx,$lf),$2,$3),$lf) }