I know some users have trouble on using KEGA.Windows 8.1 users can't play in FullScreen.I Solved problem bye me.Its too easy Just some instructions;
1)Open KEGA emulator Folder
2)Open Fusion.ini (Setting File)
3)Find ''ForceFullScreen32=0'' after make this to like this ==> ''ForceFullScreen32=1'' !!!
4) ENJOY WİTH FULLSCREEN MODE!!
I saw someone said Win8.1 Doesnt support Fullscreen!its for him
bye guys if you had a problem for it PM to me