many of you might already know this but it took some time for me to figure this out.
the search i did on this site resulted no info, and from the search results i had the impression this wasnt possible. so i am posting this just incase if some does a search in the future.
so; to run external programs try
$run_me = exec("start C:\windows\pbrush.exe");
start - is a program to run programs. and this is the help of start.exe
C:\WINDOWS>start /?
Runs a Windows program or an MS-DOS program.
START [options] program [arg...]
START [options] document.ext
/m[inimized] Run the new program minimized (in the background).
/max[imized] Run the new program maximized (in the foreground).
/r[estored] Run the new program restored (in the foreground). [default]
/w[ait] Does not return until the other program exits.
i hope it helps
works on my sys. (Apache/1.3.20 (Win32) mod_gzip/1.3.19.1a PHP/4.0.6)