Hello, this can be caused by many things.
1) Improper shut down of the computer
3) Old Age
4) Upgrading Parts & Overloading It
5) Power Supply Frying It
If you need anything else just let me know. If your having computer problems but not sure if its the motherboard or not let me know the issue and I can give you my opinion on the problem.
When replacing the Motherboard, check Ebay/Google for a better deal!
BEST OF LUCK!GOD BLESS!