What does Spyware/Malware specifically do to my computer?

Malware will perform a variety of nasty activities, ranging from simple email advertising all the way to complex identity-theft and password-stealing. New nasty functions are created every week by malware programmers, but the most common malware functions are:

1. Malware steals your personal information and address book (identity theft and keystroke-logging).
   
2. Malware floods your browser with pop-up advertising.
   
3. Malware spams your inbox with advertising email.
   
4. Malware slows down your connection.
   
5. Malware hijacks your browser and redirects you to an advertising or a phishing-con web page.
   
6. Malware uses your computer as a secret server to broadcast pornography files.
   
7. Malware slows down or crashes your computer.