I think this is the correct forum??
I thought I would mention this for the less technically gifted amongst us including me!
So must have had a power failure during the nite. One of my PC's would not switch on again. The green light on the back, however, was on.
To fix it I had to remove the power cord and the 24pin that goes to the motherboard hold the power button in for 30 seconds then leave for 20 minutes. When I went back it worked ok. Now whether the order of the above things makes a difference or not all of the things helped all i know is the pc is up and running again. Hope it helps someone else