Dell OptiPlex GX520n PC Desktop "secones beep" Questions

i remove the battery during 15 minutes and nothing happen, i reset the jumper and nothing happen. the request for a password still there nay aother sugestions? i would greatly apreciate them. well you

HP A6600f desktop, loud beep 18 secs off 10 sec, cylce repeats HP A6600f desktop, when turned on it there is a high pitch noise for 18 seconds then off for 10 secons and the cycle continues. Any ideas

Dimension 4700 wont light up the monitor. I've tried with the onboard vga.Did'nt make any difference. Remove and put back all the memory. No change. Remove the modem(pci) and the sound card(audigy 2) ...