Auto-detecting Winamp dir?

I am creating an install program for my AVS plugin(s) and would like to know if the NSI script language has a variable or other way to automatically detect the Winamp directory. If so, how?

Also, where in the .nsi file does one specify what files are to be installed?

This should do it for the finding where winamp is located problem

; detect winamp path from uninstall string if available

InstallDirRegKey HKLM \

                 "Software\Microsoft\Windows\CurrentVersion\Uninstall\Winamp" \

                 "UninstallString"

As for the specifying what files get installed ... I would read makensis.htm located in your nsis directory and also look at the provided examples located in the same directory.

Thanks...but how do I set a variable as the install dir?