FLYER1'S PROFILE

Hi I'm new to the site. My first post.
I am having problems playing vx and vx ace games in fullscreen. The games open up in window mode but when I hit alt + enter or F5 nothing happens. I've checked around the website and can't find an answer to my problem. Tried a few things but nothing seems to work. I thought maybe someone would have an answer to my problem
i5-4460 processor
8GB system memory
NVIDIA GT 720 graphics
Windows 8.1
Thanks.....