Hi we had a lightning storm the other night and I unplugged my pc's power cable but forgot to unplug my adsl modem cable. Unfortunately the lighning hit the telephone lines, frying my modem and now my pc won't power on at all. It cant be the PSU as this was not plugged in. So I'm thinking that the mobo is damaged. is this possible? How could I be sure? What are the chances that my CPU is also damaged? V.

i find it highly unlikely that the lightning damaged your PC if it's power cable was disconnected. when you power on, do you get lights, fans, anything? perhaps the circuit in the house was damaged? plugging another PC into the outlet would help you determine if you're even receiving power. If you don't have another PC, even something like a lamp would tell you if any juice was flowing.

I find it HIGHLY likely that lightning can damage any electronic device and any analog device even solid concrete. I live in a lightning strike area and can assure you that my house has been hit and near hit more than a few times.The path lightning follows never seems to make sense. It is static electricity and doesn't need electrically conductive material If you were to have had your hands on the keyboard you may have been killed. Don't fool with lightning there Ben Frankin. Any part of the system could have been damaged. Lightning is very dangerous and if it can blow apart a 200 year old old it can lay waste to your esd sensitive computer. Playing to the angels Les Paul (1915-2009)

If the modem is fried it is a good bet the PC is as well. As stated above a lightning strike can be very unpredictable. There is a chance it could be just one component, there is also a chance it could be every component. A neighbors place got hit a month ago and it literally melted his LCD monitor the only thing damaged internally however was a cd rom drive go figure. Likely I want to go like my grandfather did. Peacefully in his sleep. Not screaming at the top of my lungs like the passengers in his car. (\__/) (='.'=) (")_(")

everyone agrees that lightning can probably damage electronics. good job everyone. anyone care to address the fact that the OP mentioned UNPLUGGING their PC?

His computer was struck by extraordinarily high amounts of static electricity. I don't care if the entire unit was disconnected from any copper wire. Static in the form or lightning does not follow a path. It can jump from wall to air and back and keep going towards it's end and use an almost limitless number of paths. I agree that all proper troubleshooting needs to be performed. Also the entire home needs to be looked at. As you suggested any part of the home could be damaged from pipes to wall plug insulation. You only have to see the results of a few lightning strikes to believe what I am saying. My next door neighbor was hit one time and lost every appliance in the home. They live about 1000 feet away and it blew up my load panel in the process of them getting hit. We are talking in the millions of volts. I have seen dozens of trees blown apart or one side blown off. I have seen where an outside door light hit and went in to the home and destroyed the washing machine. The light had a small hole and the washer had a big black hole in it. Playing to the angels Les Paul (1915-2009)

Ok. The OP also stated that the unit was NOT unplugged when stated "but forgot to unplug my adsl modem cable. Unfortunately the lighning hit the telephone lines, frying my modem". You may be surprised to learn that a standard indoor telephone line is capable of carrying 110 volts of electricity. It only takes a few volts in the wrong place to kill a computer. I would have no doubt that if electricity from the strike made it to the modem it would have also made it through the modem before it died and broke the circuit. Just to test this idea try taking a 12v dc transformer and connecting it to a rj45 cable. Any 2 of the wires will do it makes no difference. Connect the other end to your ethernet port and turn on the transformer. Let me know how this works out for ya. For the OP I would recomend testing each component seperately. You may get lucky. Just because the psu was not plugged into the wall does not mean it was not part of the circuit. It is plugged into at least on point on the motherboard as well as once to each drive. If electricity was introduced by way of the ethernet port who knows the path it took from there. Keep in mind this was likely a high rate of electricity who is to say it didn't arc from one component to another. Have you opened up the case? Have you seen any noticable damage? Start with that first. Everything else here is just random guess work at best. Does it smell burnt??? Likely I want to go like my grandfather did. Peacefully in his sleep. Not screaming at the top of my lungs like the passengers in his car. (\__/) (='.'=) (")_(")