As mails bounch around some email programs (I’m looking at you, Microsoft), seems to encrypt package forwarded mails in attachments with the extension .eml. On Linux… While Mozilla Thunderbird should be able to read them (as should Evolution), it requires you have the mail application available on your machine, but I haven’t - I’m doing just fine with GMail in the browser. So far the best solution I’ve find - assuming it’s trivial non-sensitive, personal files - that an Online viewer seems to work pretty well.
VirtualBox is a free tool, which allows you to run virtual machines on a host computer. Using VirtualBox you can install Linux, Windows and other operating systems to play and experiment with. Start the process by closing virtualbox (I usually also dettach the virtual harddisk due to be resized). Go on to a shell and find the directory where the virual machines are located. If your initial harddisk was cloened from another virtualbox, you may get an error like this: