$re = '/[A-Z]:.*\.\w+/';
$str = '"msqlsum81pv 0 0 25 25 25 2 -sn D:\\\\workdir\\\\PV 81\\\\config\\\\sum81pv.pwf -C 5000"';
$subst = "";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php