How hard is to put a micro/mini ATX motherboard on an regular mid-tower ATX case? Do I need to do any changes or will it fit fine?
My micro-atx mb fits in my kick-ass iCute case sweet as. You shouldn't have a problem but may need to use those special screws that lift the mb up from the hole (You should get some with your case, they are usually gold in color)
I have built several cheap systems for people using Micro ATX boards in standard cases & not had a problem so far.
small mobo in a big case = no problem
full atx mobo in microatx case = impossible