What kind of problem do i have?

I rtecently tried to upgrade an old PC for my son.I put a new motherboard(bcm-in730se)and a new processor(amd duron 1.0Ghz).On start up the system shows as a amd athlon 1333Mhz and the computer will not come to full operation before locking up. I have tried to reinstall the operating system(win 98se)but so far i’ve had no luck. It also locks up in safe mode. HELP!