When PHP 4.0.5 (or 4.0.4pl1 for that matter) is installed as an ISAPI module for IIS 5 on Windows 2000, calls to exec(), system() and so on give errors like this:
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Warning: Unable to fork [del c:\inetpub\wwwroot\icp1sp\faxmaker\*.pdf] in c:\inetpub\wwwroot\icp1sp\admin\create_notifications.php on line 44
<-- snip -->
Running PHP as a CGI does not produce this error, and the call to exec(), system() etc. works as expected.

Here is one example that produces the error. The same example works perfectly fine when PHP runs as a CGI.
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echo exec( "del " . DIRFAXMAKER . "*.pdf" );
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