ok i need someone very clearly and preciely to run me through how to format my pc right now and load it all back on

i have some virus and cannot access any files what so ever ,all i get is this code

''this file does not have a program associated with it for performing this action.create an asscoiation in the folder options control panel''


i cant do a restore or anything as i cant access anything

so can someone pleas tell me how to format it
really easy instructions as i aint the best on pc 's

and please hurry