I would be extremely careful downloading it from anything other than a Microsoft site even if I did have a suitable licence key.
Gosh .. that was very diplomatic.
"extremely careful" is putting it far too politely.
People are absolute idiots if they download Microsoft or other commercial software from unofficial sources.
Would be a much better way to put it.
The prospect of trojans, viruses and spyware is very real indeed on torrents and elsewhere. So unless you've got a death wish, you don't go fishing around those parts of the internet.