Reformat Hardrive

Since the end of last summer I have been having performance problems, blue screens telling my to restart my computer and problems with my internet being bogged down with popups, and my homepage  not coming up. A friend told me to go into safe mode and revert my computer to before I had the problems. I did and also picked up spybot search and destroy. I also haven't been able to install or run norton anti virus. So I was hoping to finally reformat after putting it off. I have done it before, but I can't remember from the last time. Help!