Dell dimension 2400 blinking amber light

1. Remove All External Devices
2. Check the Computer's Power LED
3. If the power LED has not changed unplug the Power Cable From the Computer Disconnect All Hard Drive Power and Data Cables and power on the computer. If still no go.
4. Remove All PCI, PCI-E, and AGP Expansion Cards .
5. Remove All Memory From the Computer
6. Reseat the ATX and 12-Volt Connections . The ATX connector will be a 4 pin square connector connecting to the motherboard from the power supply and the 12-Volt Connection would be the biggest connector with a lot of colored wires.
7. If still no go.
8. Disconnect the Power Connection to the Chassis Fan
9. If the light still flashes then it could be a power supply or motherboard failure. Try a good know power supply first and if that does not fix the problem it is the motherboard. Also check the back of the tower for 4 lights lables ABCD or 1234.
Rate if useful.

Check if it does a system beep when you remove the memory.
If it beeps then your motherboard is good.
But make sure the speaker pin is attached on your motherboard so that you can hear the system beeps.

try to remove any external devices first like hard drive, cd roms, and pci expansion cards. then check if it can boot but you have to plug the memory at this time.

Hope this will help you out :)
Thank you