Compaq Evo D5 power light flashes red.

Could be the power supply. Try unplugging the internal hardisk power, the internal cd power and anything else that is connected internally apart from the motherboard power supply. This may reduce the load enough to allow the motherboard to be powered.
As power supplies age, internal electrolytic capacitors dry out and can no longer store sufficient charge to provide power. This usually affects the higher voltage rails more, so USB devices can still get power from the 5V rail.
Try a working power supply from another computer if you can or buy a replacement to fit your case.

Charger faulty or Motherboard problem.
You can check the power supply of the charger by measuring the DC voltage at the DC jack with a multimeter set to DC volts (red probe on the inner of the jack, black probe on the outer of the jack, should measure 18-20 volts.

Also check the security of the jack in the DC port, make sure it is not loose

See if the Ac adaptor has a green led on it, flashing LED indicates power not being "used " by the laptop

Gut instinct with this being a compaq is that the fault lies in the motherboard

there is problem with your motherboard

I'm afraid you need a new Power Supplies Unit. Just try an old trick first. Remove power cord from the back of PC. Press power button and keep it pressed for good 30 seconds. Then reconnect power cord and try to start as normal. If this don't work I'm afraid your PSU is dead. Good Luck

open the machine up and locate the BIOS battery. it is a small round flat battery. take it out for 20 mins and then put back in and try starting up again

Change the lamp. If red led is flashing 4 times. replace lamp fan.

Ok the lightning bolt is your power indicator: solid green-charging, Flashing green-fully charged, flashing red-low battery, flashing red three times the once green-bad battery. the "trash can" looking one is your hard drive activity indicator it will flash while your hard drive is reading and writing.

sounds like something is drawing down on your 12 volt supply drives or on board regulators. Try it without the drives connectged, and see if you can get the system to boot up(you'll just get a notice that your drives are unavailable, but you'll already know that, right?

got backup for your Dell?

turn on your computer and do nothing,, when it seems the computer stop running key in fn+f4.

try to get to the jumper next to the cmos battery in the mainboard. by changing its position for some seconds while power is off and putting it back , cmos is cleard. start the board hit delete to enter setup and exit saving chages.