Scrabble Software
Earlier this year I purchased Scrabble software from Big Fish Games for my Windows 8.1 computer. It runs great and I have been enjoying the game immensely. It uses a North American version of the Scrabble Dictionary.
So if there are any Scrabble fans out there looking for a version of Scrabble that works with Windows 8.1 consider Big Fish Games. I should also point out that they frequently offer a significant discount on your first time purchase so look for the discount code. If I remember correctly I only paid $2.99.