Hi Charlie,
What was the message from the fatal error when installing newer versions? 6.0.25 was a minor change from 6.0.24, so since you were having issues with that version as well, there may be a change on the server
Wordfence isn't officially supported on Windows servers, but we have heard of others having success with prior and current versions. Most unusual issues we see on Windows are due to running an older version of PHP, especially 5.4 or below. Do you know what version your site has?
@drbellerive: If you are using an older version of PHP, can you try updating PHP itself as well?
-Matt R