Try replace CMOs battery with a brand new CR2032 battery and clear CMOs settings by jumper reset on motherboard.
a problem of red light on motherboard stays on all the time , i hv done testing the flowing : {OptiPlex 390 } 1- rams 8gb for each slot . and those are new ones 2-power supply is working right, if u push the test button turns green and fans working with an orang led light  with the power button showing. also tested the button is working great. 3-cpu tested it with another pc is working good   any help!!   .  
red light on motherboard