Using RegExp to find all occurrences of a word in a string.

Find all occurrences of a word in a string where the word can be at the start of the string, the end of the string, or anywhere in the middle, and the word must not be part of any other word.

This works outside of Windows:

(?<=^|[^A-Za-z])(Word)(?=[^A-Za-z]|$)

But does not produce any results inside Windows. I think it has something to do with look-behind logic but, when I remove that part, it still fails:

(?=^|[^A-Za-z])(Word)(?=[^A-Za-z]|$)

Kevin