I'm confused about x64 and x86. Someone help me understand?

x64 and x86 are identifiers for different types of processors.

x86 is for 32 bit, and x64 is for 64 bit processors.

It is important to get the right one, because the software contained in each build (64/32 bit) is made for the kind of computer you have. Not knowing what kind of software you are running right now, I don’t think I could tell you how to find out. Look for a detailed hardware overview. The device manager in Windows is a great place to start. The BIOS might be able to tell you something as well.

I don’t know about all of the issues with the server OSs, but I do know that Windows has been stuck in an awful 64 bit catch-22 for the longest time: there are no drivers for 64 bit because no one uses it because there are no drivers… Buyer beware.

If I had to guess, I would have to say that a general purpose tower that you are trying to put Windows server on is of x86 architecture.

I’ve never had a problem installing an x86 OS on an x64 processor, so you only need to worry about having x64 software if you only have a x86 processor. Today you’d probably be buying a x64 processor anyway. I use Linux and have used a x64 OS for about 3 years now without any driver problems, so basics like video, disks and networks will be covered. The problems generally arise with hardware that is Windows specific (i.e. no application software for Linux or Mac)