Can't help you with Win 7, 8, or 8.1, but I was running my layout on an old laptop running XP.
I only use the old lappy for my railway (plus a few other odds and ends) with LGB MTS 6.0 software.
LGB software was written by Stellwerk, and they did later versions which run on later Win OS.
Here's the linky....
http://www.stellwerk-software.de/en/