The following example PHP script works fine when run from the command line, but fails when run via IIS.

<?php
$wsh = @new COM('WScript.Shell') or die("Cannot create instance of Windows Scripting Host!");
$key = 'HKLM\foo';
$v = $wsh->RegRead($key);
echo "<br> Got $key = $v\n";
$v = $v + 1;
$wsh->RegWrite($key,$v);
echo "<br> Set $key to $v\n";
?>

The error returned references the line containing RegWrite.
----
Got HKLM\foo = 2 
Warning: Error in php_OLECHAR_to_char() in c:\asg\webmanager\test\x4.php on line 7

Warning: Error in php_OLECHAR_to_char() in c:\asg\webmanager\test\x4.php on line 7

Warning: Invoke() failed: Exception occurred. Source: Description: in c:\asg\webmanager\test\x4.php on line 7

Set HKLM\foo to 3 
----