Can't Play Games On External SD Card [ Android ]

Hi Tom's Hardware!

I am unable to play plenty of heavy games (700mb & above).  
I have installed File Manager HD for my Tablet.
My Tablet's name is Acer Iconia Tab a100
As you know that tablets lack options regarding External SD Card, I only have a option to safely unmount it.
Another weird thing is that whenever I move a game to external SD Card and then bring back to it's place , it just won't run! Directory ( sdcard/android )
So please help me out without rooting my Tablet..

Thanks,
Regard,
Men_In_Black