I installed Motherboard Monitor 5 and installed a new processor fan... but the temperature it displays are... cpu=-128c and case=-128c.
can someone please tell me whats happening here? either the software is corrupted or something else is wrong... appreciate your help and thanks in advance.

I would have to say the the software is corrupted or not the right version for the motherboard your cpu won't work at those temps and would be damage. and you case and cpu temp shouldn't be the same unless you got the computer in a oven that on unlikely.