You would have to be familiar with the various build numbers. I'm running
build 12.0.4407.1005, and I know it's B2TR. Since you're running a much
earlier build (12.0.4017.1006, contrasting 4407 with 4017), and there have
been only two public builds available, B2 and B2TR, then it follows that you
must be using B2.
But, trust me. B2TR is much improved over B2, and well worth the download.
Note that it applies as a patch and not a whole new installation. The only
significant problems I've heard of folks having with B2TR are:
1. Norton's Office Plug In (which isn't really needed since Norton already
monitors all files that get put onto your computer) can keep you from
opening files, so you should disable it, and
2. Building Blocks.dotx is now a different format. So, if you get an error
message about that file, you would need to delete your existing user-created
Building Blocks.dotx file before Word 2007 B2TR will run without an annoying
error message.
Cheers,