HP mt42 Win 10 LTSB incompatibility with Office 2016

[BLF609]

Have an HP mt42 running Windows 10 2016 LTSB. It's up to date with the monthly patches. I use it as a laptop, not a mobile thin client.

I've installed many of the usual programs one would find on any laptop (Adobe Reader, Chrome, Driver Easy, Glary Utilities, ccleaner and others including LibreOffice). All installed perfectly and work fine. 

Recently I decided I wanted to have Office 2016 instead of LibreOffice (just easier to deal with).

And it just won't install. Gives errors at the beginning of the installation as if there was a previous Office version. I've had extended support sessions w/ Microsoft and they tell me Office 2016 Pro is compatible w/ Win 10 2016 LTSB.  They've done remote access cleanups, etc, tried downloading different Ofice images, etc, etc. And it still gets the same install errors at start up. Doesn't matter whether I try to install from an iso image or an attached DVD drive. MS has validated my product key is good (and that's not the kind of error I receive). 

The last tech suggested I update to a later version of Win 10. Will a 'regular' Win 10 (i.e. Win 10 Pro) run on the mt42?  I'm fine with doing this, but want confidence I won't end up bricking an otherwise good device.

Is there some sort of trick to install Office on the LTSB version that is needed? I've turned off all the write caching stuff; it just operates as a laptop using the main SSD.

Thanks.

[BLF609 · Accepted solution]

And I solved the problem. Another post gave me a hint. I had changed the environment variables to not use the Z drive as a temp location. But I had not changed them in all the places they appeared in the env variable settings.

Changed them all to point to the C: drive and everything suddenly worked fine.