I've been using Windows 8.1 for a few weeks now, but since yesterday the mouse cursor stopped being locked to some games (Watch_Dogs, Dead Island). Watch_Dogs worked just fine two days ago, didn't try Dead Island before. Other games like Loadout work just fine.
I didn't install any new drivers (even tried reinstalling my graphics drivers though).
I have a Nvidia GTX 770, but as I already said. I installed the new driver a few days ago when it came out and Watch_Dogs worked just fine with them.
Best Answer
I had the same problem when playing TES:V. After some research I found this program called Primary Lock. I know the website looks really fishy, but it is completely free of malware and viruses.
All it does is lock your mouse to the main monitor for as long as the program is open.
Primary Lock