If for some reason you do need to use the shell command, try something like this.
shell '%comspec% /c start <PROGRAM>'

By using start, you cause the program to execute and return to the script. BTW, this also works if you want to launch a web page from a script.
shell '%comspec% /c start http://server.com/webpage.html'

This will launch a web page using the users default browser.

mpearce@nbase-xyplex.com