I have Dell Dimension 5150 that was PURCHASED in Dec. 2005. I have Windows XP operating system. The COMPUTER sometimes was shutting itself off or would go to restart. I was able to restart without problem most of the time. But sometimes it could not be restarted. The switch that turns the computer on would start blinking (yellow / orange) when turned on and stopped right there. I had this problem many months back and my neighbor (he is not a computer engineer but is a software developer) told me to unplug all peripherals including the inner CD drive. Then "drain all charge" by unplugging power and pushing the start button for a few seconds. Plug power back on and start and start plugging peripheral starting with keyboard and mouse since I would need them to start the computer. I was able to start the computer using this procedure. For the last few days the problem had occurred many times and I am having problem with this procedure ALSO. I was able to start a few times by going through that process.

My neighbor also suggested defragging my computer. So when I was able to start the computer I did a fresh virus scan and did defragging also. It took me a total of 5 or 6 restarts to go thru the entire process. Every time I was afraid that the m/c will be really/fully dead since the m/c went down while doing these processes. No virus was detected. Now I cannot start the computer alt all. All that HAPPENS when I go through the above procedure is that the switch that turns the computer on STARTS blinking (yellow / orange)

If you can help in any way, please do.
Thanks.
First question is have you opened and cleaned the pc in the four years you've had it?......If not open the case and clean out all the dust and dirt inside.

If the inside is not dirty, consider swapping in a known good power supply.The computer has been cleaned.

The lights still show up including the main switch which blinks when turned on. Is it still possible that the power supply has gone bad?

Thanks.Yup, absolutely.......slight variances in DC power will cause your symptoms while allowing lights and fans to work normally.

To add to this from the Dell5150 manual...

IF THE POWER LIGHT IS BLINKING AMBER — The computer is receiving electrical power, but an
internal power problem might exist.
• Ensure that the voltage selection switch is set to match the AC power at your location (if applicable).
• Ensure that the processor power cable is securely connected to the system board (see "System Board
Components

http://support.dell.com/support/edocs/systems/dim5150/en/om/WD846A02.pdfThanks
MGRG1959clear cmos might helpQuote from: smeezekitty on August 16, 2009, 02:10:16 PM

clear cmos might help

the bios can take up bad settings and cause intermitten boots
it happened to me
never had a blinking light though