Microsoft is currently getting cozy with Dropbox and now you can get 100gb of free storage added do your existing storage for a full year.
All you need to do is sign in to OneDrive (or create an account) and let OneDrive send a file to your Dropbox account to verify you are a Dropbox user. You will then have 100GB of space added to whatever you currently have available. (for 12 months)
Here is the promo link