Not a virus, because one of the features of a virus is that it self replicates. This is just a delete command, and it doesn't show "how easy it is to write a virus for Windows" - if that's the case, then "rm *" is a 3 character "virus" for Linux, or "sudo rm -rf /" for a more powerful 10 character variant.

http://en.wikipedia.org/wiki/Computer_virus