reformatting?
it deletes and clears your PC of EVERYTHING. windows the works.
then you have to go thru the process of installing windows, and drivers. ie, motherboard, graphics. by the end of it you get your PC back into the original form you bought it in.
very easy to do if you know how and take around depending on the speed of your PC and the size of your drives. around a half day to get it fully up and running with the programs of your choice.
be warned tho. everything goes. so backup of data on an external drive is essential.
and just to clarify, i am not a PC wizz, i learn this to save up on having to send in my PC in everytime it got slow or crashed... saved me alot of cash so far!
best way of finding out more would be thru google..
its how i learn't... i did get stuck in places the first time...
and made errors.
but i had help nearby with friends who knew what they were doing...