I have a PC for while and it worked just fine. Since last week, I cannot defend from some chain mail spam and all sort of email hoaxes. I don't know how they find me, but every day it got worse. Every new day I have more and more spammers attacking me. I heard that Government even issue warnings on email scams. Why spam exist?
The history of internet spam is almost as old as internet itself. It starts as a way of computer marketing. There are few things that you have to practice if you want to avoid the spam. If you don't want to infect you should respect few basic rules of cyber space hygiene. Never register your main mail address on any email list unless you have recommendation from other users. If that list belongs to spammers, they will trade your address to other spammers. That way you will find yourself in the situation like yours now. The other thing is to avoid opening any mail from unknown user or with "best offer you can get". That also worth for email hoax like "You're a winner" or "Your ticket win on our lottery" etc. In your case, because you are already infected, you will have to find the external cure for your illness. I could personally recommend you the program Mailwasher. That program intercept your emails and delete the spam for you, therefore you do not need to deal with it.