After following the instructions numerous times and checking folders and files I kept getting Internal Server Error 500 - I thought I had just wasted $19.99
I checked the PHP software settings on my hosts server. I contacted them and was advised they would not adjust any memory or time-out settings.
After numerous adjustments to the folder/file settings this worked for me.
generator folder permissions set to 755
index.php file set to 744 and runcrawl.php set to 744
enter your domain name [external links are visible to admins only] in the address bar of your browser and you should see the xml.sitemaps standalone generator configuration
Hope this helps anyone else with getting the script to run.
[external links are visible to admins only]