Plz tell i dont want to go to technician.?

I got some good answers,but really dont know wht to do or follow. Wht will be the cost of new Hard drive or old can be repaired at wht cost.(HP laptop dont know model) Should i install new antivirus first or try to recover deleted files,documents and microsoft windows ,google talk etc by visiting websites of recovering files.One thing more from 2-3 yrs external mouse is also not working in my laptop,someone told it will cost thousands to repair external mouse( wht we use in general computers )for functioning in laptop.