The antivirus software that came with your computer has been out of date for years, so it's likely a virus on your PC is trying to spread by e-mailing copies of itself to people in your address book. Get a new antivirus program and run a full system scan to find and remove the virus. The free AVG antivirus software is available from www.startribune.com/a1443, and programs are available from Symantec and McAfee for a fee. Regularly update the software online to keep your PC from becoming vulnerable to new threats. You will need to repurchase the Symantec or McAfee software once a year.
You also should protect your PC with firewall and antispyware software. Download best antivirus software