i have an hp s3500t with a foxconn mobo ...i turn it on i hear the hard driver come on the cpu fan workni then this long beep ,,,for about 18 sec then stop then beep again took out the memory there good check the hard drive it good ...so what it causing it to beepin i been on hp web site check the beep code that still didnt help ..
More aboutmotherboard test them
Basically you test the motherboard by eliminating any other source of failure. If you've got another psu, try that first and hope. Don't know how successful you'd be replacing the mobo.