The power button on a compaq presario desktop is not working

change ur mouse ...restart cpu

Try clearing CMOS. Take the battery out and press and hold the power button for 30 seconds. If that doesn't work disconnect or change out drives and memory one by one until you find the reason your pc won't POST. Once you can at least get to BIOS you've found your problem.

If all plugs etc are connected correctly and it is in standby, press the power switch momentarily and it should boot up. If not press the power button for 5 - 6 seconds and if that doesn't work there is a problem with possibly the power supply.

Welcome to FixYa
Dear user
Perform a Hard Reset first.
Disconnect devices including USB devices and media cards. Disconnect the AC power adapter, remove the battery Press and hold the power button 15 seconds . connect the power adapter -do not connect the battery- Press the Power button, Look for blinking LEDs near caps lock and num lock keys, and Listen for sounds of a disk drive and fan turning.

Hope this helps...Thanks for Connecting FixYa...

Disconnect all cables from the computer. Press and hold down the power button for about 20 seconds. Reconnect only the power cable and try to turn on the computer on pressing the power button If it turns on then good otherwise, switch the power cable of the computer with the power cable of the monitor as they are the same cable as the power cable could be bad but this rarely happens. Open the computer and see if you see any light on the motherboard, if you do then the power supply is bad. If you dont then both power supply and the motherboard could be bad.

It might be the motherboard that needs to be replaced or the power button.

Hold it down for 15 seconds,if it goes totally off,change your power setting in the control  panel

It a issue with the power supply or the SMPS. Change the SMPS of same capacity and then it should work..............sodeep

hi,
The machine is getting the power but no display.This seems a RAM or motherboard issue.
1.Press and release NUM Lock after turning on and if it is responding this is a RAM issue and if not then the mainboard issue but before all refix the RAM once.
Thank You.

Actually you do want to hear one beep.
This is POST. Power On Self Test.
No display is a video problem. Swap the card for a known good video card. You should be able to get into the BIOS with that. Presario’s are quit.
While in the BIOS see if the HDD is shown. It doesn’t hurt to check the connection inside. Please keep yourself grounded when inside the PC. For the Compaq Presario S4020WM site go here:
http://h10025.www1.hp.com/ewfrf/wc/softwareCategory?lc=en&cc=us&dlc=en&product=326832&lang=en&