Nskaran its good that your PC come to normal after 3,4 attempts. Now Read it carefully and do take care while doing what I am going to said, First of all if you have any the following:-
1. CVT (Constant voltage stabilizer )
2. UPS (UN Interrupted Power supply)
Now tell me if you are using te system without these Power out put units. If yes the you can Try first using any of these products to check if system gets Normal,Because in Summer mostly power cuts + Load shedding give very low Voltage due to which some time system didn't work properly.
Now Next step is if you know some thing about PC hardware means its main components like CPU, RAM, HDD etc, For giving a check you have to get out the RAM modules from its RAM SLOTS and just clean with a soft cloth it should not be wet ? So after cleaning the RAM Modules Insert them again in the RAM slots properly. Now start your PC and see if the problem gone.
Most probably the problem should be gone after these two Attempts. If it does not help you then please your have to install fresh Window's,Do tell me further if Problem Persists ,Then I will suggests you more on that.ok bro.. make a habit to clean your PC after 2,3 Month's.