Warning: exec() [function.exec]: Unable to fork [ping 10.8.1.70] in c:\Inetpub\wwwroo

[chchar]

Hello,

I'm using PHP Version 5.0.4 in IIS5, Window 2003. When I
execute my script, it prompt me the following error :

Warning: exec() [function.exec]: Unable to fork [ping 10.8.1.70] in c:\Inetpub\wwwroot\switch.php on line 62
Below is my script :

<?php
$line1 = exec("ping 10.8.1.70", $output);
exit;
?>

Any help will be appreciated...

Thanks.