To fix the problem, follow the steps below:
- Open Outlook Express
- On the menu, select TOOLS and then OPTIONS (a small window till open)
- Click the SECURITY tab on the newly opened window
- Uncheck the box that reads, "Do not allow attachments to be saved or opened that could potentially be a virus".
- Click the OK button to save the changes and close the window.
That should fix the problem. Try opening your attachment again.
If this didn't fix the problem ... there may be another security setting somewhere else that needs to be reconfigured.