|My brother had a desktop computer that had it's power supply damaged when a circuit breaker tripped. It never booted again with that power supply - replacing it restored his system to working again. |
He had the computer plugged into an anti power surge / spike power bar at the time, but he may not have had everything that plugs into the computer that plugs into AC plugged in to it.
You have to have everything that plugs into the computer that plugs into AC either directly or via a AC to DC adapter, AND the cable that connects you to the internet if you're using (wired) network cable(s), plugged into an anti power surge / spike device, and the device should be of better quailty - e.g. it should have a warranty that compensates you for attached equipment damage. Even then, sometimes things are damaged.
If you're fortunate, the probable power spike or surge that occurred when the breaker tripped may have damaged only the power supply. If you replace the power supply, your system may work fine again.
A side note - el-cheapo power supplies are much more likely to be damaged by an event like yours. Better power supplies have protection that may prevent the power supply from starting up properly for a while after the PS is exposed to an event like yours, then it will start up fine. If you have a quality PS brand, or in any case, try unplugging the AC from the power supply for at least a half hour, then plug it back in again - it might then work.
NOTE that if you're not in the US or Canada, e.g. the computer was bought in Europe or the UK, the power cord for the PS may have one or two fuses in it, probably on the plug end, that may have blown.
Failing or dead power supplies are common and can cause your symptoms.
Check your PS.
Failing power supplies often partially work, fans and hard drives may spin, leds may come on, yet you may get no video and the mboard will not boot all the way.
See response 4 in this:
If it is failing or dead, you can usually replace it with any decent standard sized standard ATX PS with the same capacity or greater.
Standard (PS/2) power supply size - 86mm high, 150mm wide, 140mm deep, or 3 3/8" h x 5 7/8" w x 5 1/2" d , or very close to that, though the depth can be more or less for some PSs.
Don't buy an el-cheapo PS.
See response 3 in this:
Did your wife by any chance vacuum the computer?
DO NOT use a vacuum cleaner to do that - they produce a tremendous amount of static electricity when running, and anything connected to them can discharge that to your components.