Computer is not booting

Hello,
I am facing a situation that my computer is not booting up. My monitor wakes up , fan runs in smps a green light on cpu turns on, mouse lightsup and keyboard light also turn on. Before a few months i rreplaced my smps with another one with some issues as similar like this . In my monitor after this replacement a menu before going to boot comesup and says as text your powersupply not detected, just like this something something..., And says to click F1 to boot . I just simply clicks f1 to boot and after clicking f1 compiter works smoothly . But now at the top left some units run and finally comes to rest as 1016MB . And not going any more . Not saying press F1 to boot .. and not boots . What do i do now ? Plse tell me any suggestions. No money to bring a technition help me please i am using and assembled set with windows Xp