I just put this little script together with AutoIt.
Simply put the 2 files in the rr root, skin folder or where you want them. Name a song to intro.mp3, and put it in the same location.
If you have RR start at windows start, simply put a shortcut to the PlayIntro.exe in the same place (startup folder ect).
This way the intro song will start at the same time Road Runner begins loading. While RR is booting, I do not know of any easy way for it to play a song, as it in not "ready", as well as Winamp is not ready, for audio playback when it is loading ect.
This script works independent of RR and Winamp, and will start playing the audio virtually instantly when run.
I included a StopIntro.exe, you can use that when testing, as well as if you want to add to ONSKINSTART to stop the audio once RR is loaded.
Again put both files in the zip, as well as your Intro.mp3 all in the same folder.
Hope this helps!
Play intro sound startup sound road runner starts