Virus affected need to know what to do

Hello,
My pc has never got virus before. Recently It is affected by virus and I am in a fix. I need someone to tell me what to do what are the alternatives what to do in order to keep my files safe.
I need many of the files so I really cannot do a full flash or set up without knowing what will happen to them if I do. please help me out of this trouble.
Lambert Gaston
