You can to run Windows XP, Windows Vista and Windows 7 on that board. It also will support bot the 32 bit and the 64 bit versions of each OS.
Check out this link to your exact board on the ASUS website.
http://usa.asus.com/Motherboards/AMD_AM3/M4N68TM_V2/
Click on the "Memory Support List" tab to identify the memory models that ASUS has verified to work with your board.