Windows 7 x64. 8GB of RAM here. Enough for now.
definitely an improvement from Vista! I had the bug where it would hang if you ran Windows update & the OEM never gave me the install disk(the Vista system was from Argos before I got my shit together & built this bad boy)
I've only encountered 1 old game I had to use the Win XP VM for (Dungeon Keeper 2); Just about anything else can be fixed by compatibility mode & a little trial & error.
I built this thing to play games & kick ass at it(I am one of those freaks who value both graphics & high framerates in equal measure, no matter what the game - so hate on me, whatevaaaaa, you would if you could & ya know it)
There is no reason whatsoever I can think of to get Win 8, it is totally designed for tablet computers & brings nothing new in terms of DirectX(gaems!!) or functionality in any meaningful sense.
As for WOW64 having problems? Wha?
You ARE using 64-bit drivers on your 64-bit OS, right??