Can't tell you, really.
Postings about this in the boards here are quite fuzzy concerning this.
Majority says, they couldn't get it to work on any win7 and above, others say it worked on 32 bit windows, but none of the 64 bit versions.
Nobody really did some research into this AFAICS, nor detailing about steam vs non steam or such.
So, it could be that it's about steam vs. disc version or, more likely, IMVHO, that one of your win 8.1 is 32 bit while the other is 64 bit.