I saw that some 64 bit editions of Windows can support like 128 gigs of RAM.?

Question

Are there any mobos that can actually handle that much? If not, What's the limit?

And do you think I could make money by making custom computers for the neighborhood, and upgrading other computers too?

Answer 1

The max I've seen any "comsumer" level boards handle is 16

GB of ram.   Typically most boards are still maxing out at 4 or 8GB now.

Answer 2

The current max is 16GB but this is really due to the space limitations of most motherboards and the maximum DIMM size available.  Most motherboards only support 4 DIMMs each of which can be 4GB DIMM and some will support the 16GB total, but lets be realistic, why?  8 is the common maximum and it is more then enough 100% of the time, there really is very little reason to even have 8GB of ram let alone 128GB or even 16GB.