http://g.ho.st/

"G.ho.st offers every person in the world a free Virtual Computer (VC). G.ho.st is simply pronounced "ghost", an acronym of Global hosted operating system (written G.ho.st with two dots because a URL (web address) must have dots!). The G.ho.st Virtual Computer includes almost everything you would have in a physical computer - a desktop, file storage (like a disk drive) and applications (apps). "

  

Go to http://g.ho.st/ and give it a try, login through the guest account