• Open O.E. and click the menubar -> tools -> options.
• Click on the security tab of the window which opens up.
• In the first section "Virus protection", take the tick out of the box that says "do not allow attachments to be saved or opened that could ...... "
• Click apply and ok and restart Outlook Express.
• You should now be able to open the attachment(s) .

NB attachments with the extension exe or vb ( e.g. name.exe or file.vb ) are executables and probable viruses so you should never open them unless you are absolutely sure of their origin. When you open an executable you are completely at the mercy of the person who wrote it - one click can totaly destroy your computer and all the data on it. It is a bad practice to email these files in this state in the first place - proper practice it to compress them with a program like WinZip or WinRar first.

Remember that image files like jpg, gif, bmp ; music files like mp3, rm, ram; video like mpeg, mp4, mpg microsoft office files like doc, wdb, ppt and xls and web files like html, url, xml, and xhtml along with many other file extensions are completely safe. If in doubt do a google search for the extension and try to determine if it is a program or a file ( files are usually safe; programs {executables} may not be ).