A new virus is out that can infect photos and picture files. While this particular virus may not spread like wildfire, it is a dangerous sign as it marks a new type of file that can become infected. Previously, movie files, pictures, and text files were considered "safe". Now more than ever, you need to make sure that you know who sent you an email, that the text of the message seems to be from the person who sent it to you, and that the attachment is safe.
If you're looking for a good, free virus scanner, I recommend AVG from Grisoft. It is compatible with Outlook/Outlook Express and can be set to certify your incoming messages as "virus free". Definitely a good thing. Also, AVG will update itself over the internet as you direct or, by default, every 15 days or so. Also a good thing.
Two last tips: 1) Do not open attachments from strangers. This is somewhat akin to not taking candy from strangers, and 2) Update your virus scanner regularly. If you haven't updated your McAfee or whatever you might have, open the scanner and follow the options to update the "dat" (data) files. Updates are free for almost every program.