Hi Paul,
From what I can see on various searches HTA files are Microsoft Internet Explorer specific. I didn't see any mention to them being used on Macs, but if any application would be able to launch them it would be the Mac version of Internet Explorer 5.2 (this is no longer developed by Microsoft and hasn't been updated for a couple of years now).
Microsoft no longer have it available for download, but this site appears to have it still:
http://mac.softpedia.com/get/Internet-Utilities/Internet-Explorer.shtml
Note that there also a few mentions of security implications for HTA files in the searches I did, so if that version of IE can launch them, make sure you know and trust the origin of the files.
[ Edit: The only way the Intel chips would help in this case is if you installed Windows on the machine in question 🙂 ]
