Because you checked, obviously your computer is above the minimum spec's. Then, somethings is wrong if your computer won't run Tane SP2 HF1. There are a number of things that could be affecting performance/frame rates.
As a suggestion, try turning as many Tane settings a low as possible, with things like "Shadow", etc, turned off. See how it runs then... If it runs OK, then you could then start raising some of the settings until you hit that "sweet spot".
Try turn everything that's not essential running in the background "off". Eg; A/V, etc...
Not knowing what your computer spec's are, something as simple as putting in a better video card in, or increasing the amount of ram,
(assuming you only have 2 or 4 gigs) can make a world of difference.
(Especially the video card).
I'm not to sure what N3V refund policy is. Good luck with that one...
Foot note; Shane, the person you barked at, is one of the most respected member of the Trainz community. He's gone out of his way to help 100's of Trainzers over the years. Here's a small sample. He went out of his way to write these tutorials to help us out, (especially the newbies);
https://forums.auran.com/trainz/showthread.php?87067-Full-Listing-of-my-tutorials-as-of-20-03-2012
My suggestion, and it is only a suggestion. If you plan on sticking around, (& your very welcome too) it wouldn't hurt to acknowledge that you barked at Shane and offer him a simple apology. If you plan on jumping on your bike, good luck with your refund and your en-devours...
Cheers, Mac...