[Jaruzel]

HTAs are a subset of MS's Visual Basic Script language with a smattering of built-in HTML support.

If you are a masochist, it's entirely possible to write a full application as a HTA. I once had to do this when I needed to explore an organisations Active Directory, but they wouldn't install the AD Admin tools on my Laptop, or give me local admin. (For those that know AD, it was a 'Users & Computers' clone written entirely in HTA. I used Notepad as my IDE)