SmallBlaze :
USAFRet :
Case - "It supports the latest ATX and micro-ATX motherboards..."
Motherboard - "ATX Form Factor Dimension: 30.5cm x 22.5cm ( W x L )"
What specifically is not fitting?
The board mounting points don't line up. The left and middle line up perfectly, bu the right side mounting points are off by about 1/2 inch
Well...either Biostar or Cooler Master is telling fibs, or something else is not right.
With the motherboard out of the case...
Measure the actual distance between the mount holes on the mb
Now measure the actual distance between the mount holes on the case.
If there is an actual difference, you have a problem.
If not...you just need to work with it more.