Keeping PC Virus free
1. Have a reliable self updating anti-virus program like Norton, Mcfee etc. or the free one from grisoft.com
2. You can do a free online check at housecall.trendmicro.com/
3. Never open an attachment from someone you don't know. Your anti-virus program should be able to detect most problems.
4 Try to avoid using Microsoft Outlook it's too vulnerable to hackers and viruses. You can download other software like Eudora etc