Check for POST beeps and this might point out the problem. If there is no POST screen or you dont see the BIOS screen when booting then could be a problem with mobo. try getting another mobo and fixing the other components together and see if this helps. this will help show if the mobo is the problem.

This kind of troubleshooting would just require a step by step process to eliminate all causes and try to isolate the offending component. As he rest have said it seems to be a problem with the mobo. seems to be fried.