Alhamdulillah, I have manage to combine 64-bit and 32-bit Windows 8.1 installer into single installer known as AIO(all-in-one). I really want to do this because not everyone have same computer specification to install either 64bit or 32bit. And I dont want to reformat my thumb-drive to create bootable USB for windows 8 64bit/32bit. So, I "Google" around to find tutorial on how to do Windows 8.1 AIO .ISO installation file and I found one, and spend more than 2 hours to try it out. So let me show you,how I did it.