The latter is your 32 bit folder in which most of your 32bit programs will install. Thus the fact that you have C:\program files, and C:\program files(x86). The game folders themselves are labeled 32bit.so I don't think the steam version has 64bit, or possibly the map editor is 64bit (i would hope), but either way 64 bit microsoft non server operating systems will operate in both 32bit and 64 bit environments.
I installed on a 圆4 win7 ult rig and by default steam installed the game in the x86 (32bit) folder.
