Happened to me and still kicking myself about it!

Be careful when you open the music, games or video app provided by windows if you, like me are now using a different Microsoft account than the one you are using with your gamer tag on the xbox.

Transferring gamer tags is possible with a little work. A guide can be found on Xbox.com/accountswap

The problem here is that, if Microsoft automatically created a new gamer tag for you (wich it does when you open the app), or if you already have an unused gamer tag associated with this Microsoft account, you will have to make a dummy account to transfer your gamertags in 2 steps.

This is where it gets gruesome because newly made Microsoft accounts can't transfer gamertags within the first 30days of creation.

Basically just waiting for the days to pass by the finally be able to organize both of my accounts properly and sync up my laptop and xbox. Damn...