Outlook Express and Outlook 2000-2003 have an anti-virus feature that blocks potentially harmful attachments from being opened. Unfortunately, you can't open the attachment even if you know it's safe.

Before proceeding, you should check to see that your anti-virus software is scanning incoming mail, and that your subscription is up-to-date. Anti-virus software works by looking for signatures of known viruses, and if your software is not being updated with the latest signatures, you really don't have any protection.

Modifying Outlook Express to allow attachment viewing is straightforward. You can find detailed instructions here.

Outlook 2000-2003 is a little more complicated. If you have an Exchange server, your network administrator can make the change for you. If not, you will need a third party plugin to do the job. It is available as shareware from Slovak Technical Services among others. There are also many plugins available through the download.com web site. Search for "Outllook Attachment."

Note that in most cases, the plugins allow you to change the security settings for different file types, but you must tell it which file types to accept. Check the software documentation for the plugin of your choice.