If you download alot of things from the Internet or use e-mail the first thing I would suggest is to get yourself a Virus checker. They are very cheap and could save you alot of heartache. If you decide not to purchase a Virus scanner at least do the following. Do not open any files attached to an email from an unknown, suspicious or untrustworthy source. Do not open any files attached to an email unless you know what it is, even if it appears to come from a dear friend or someone you know.
Some viruses can replicate themselves and spread through email.
Better be safe than sorry and confirm that they really sent it. Do not open any files attached to an email if the subject line is questionable or unexpected. Do not download any files from strangers. Exercise caution when downloading files from the Internet. Ensure that the source is a legitimate and reputable one.