so whatever was done didn't work. Can you tell us who did the repair and what they did. Also, it would help to know something about the model and age of the desktop. Unexpected shutdowns are often linked to power supply, heat, poor electrical connections, etc., but other issues can cause this. Troubleshooting steps would include booting to just the BIOS or safe mode and waiting to see if the same happens. This helps determine if it's a hardware cause. Post back more information if you can.
My computer, an Asus desktop, with Windows XP, sometimes shuts down immediately, like it is powered off. I had it repaired once, but the same problem came up again since two weeks. It can happen multiple times per hour.
What's likely to be broken? I'd like to fix it myself this time, what do I need?
Thanks, I appreciate your help.