There is way to write a statement that will honor the wildcard, case insensitive. Try:
names of find files “*.exe” of windows folder
Another way you might want to try:
names whose (it as lowercase ends with “.exe”) of files of windows folder
However I would be careful when using ‘descendant of root folders of drive’ because this query can take a really long time. I would suggest using it only for folders that don’t have a lot of descendants. For example I ran this query in my relevancedebugger:
q: exists descendant whose (name of it as lowercase ends with “.mp3”) of root folders of drive “c:”
A: True
T: 10547.125 ms
I: singular boolean
This query took over 10 seconds to evaluate in my relevance debugger. If you factor in that your BES client (unlike relevance debugger) is using only about 2% of CPU you can see how relevance query like this would be detrimental to your BES client.