What I'm trying to tell you is that you don't need to read from Winamp to get the MP3 information, all you need is the filename and the $sound identifier and you'll be able to turn all of the following details:
album, title, artist, year, comment, genre, track, length, version, bitrate, vbr, sample, mode, copyright, private, crc
If you insist on having the information sent by Winamp, there are several addons for both Winamp 2.x and 3 which will use DDE to send a message to mIRC whenever a song is played, as well as numerous DLLs for controlling Winamp and returning information, amp_in.dll for example.