I brought up a command prompt to make sure that it was installed globally – I typed tsc -v which is a version check command. It came back with 1.0.3 which is a really old version of Typescript. This was strange because I had loaded a new version using npm so there was no reason why it would be pulling down an old version. Then it hit me..
So I peeked at my environment variables and noticed there was an entry already for Typescript.
It most likely came when I installed the full Visual Studio IDE.