Exec as user

I have been looking through the docs and found no help on either finding which user the EXEC'ed commands run as, or how to specify which user they should run as. I tried exec, system, and passthru running a batch file that would write %USERNAME% to a file. And all three functions wrote nothing. They would however write "hello world". Has anybody else run into this. I tried exec("test.bat"); test.bat: echo %USERNAME% > test.txt when run from a command line it resulting in "Charles" when run from a webpage it resulted in "ECHO is on." if I added a line "echo off" above the echo username it resulted in "ECHO is off." again only from the webpage. In essense I need to update a DNS server through a web page. It works if the script is local but not if it has to update a different server. Charles Killmer Windows 2000 Server, IIS 5.0, PHP 4.1.0