Boot while tapping F8
When you reach the choices of Normal, Safe Mode and so on, pick "Command Prompt Only" (I think it is choice No 5).
At the C:> prompt, type ............. scanreg /restore ......... and press Enter
You will reach a screen which offers to run a previous copy of the system, usually you choose one of 5 previous dates.
Pick a date just before the power cut and enter that. If you are lucky it will not find any errors this time and go straight through to the way it looked when all was sweetness and light!