About a year ago, Microsoft gave away 100GB of OneDrive storage to anyone who signed up in time. It has been around one year since the giveaway so the bonus will be expiring soon.
To check if your account has the enthusiasts bonus and when it will expire, log-on to OneDrive.com and click on the Get More Storage button in the lower left corner. Under Your Additional Storage, find Enthusiast Bonus followed by 100 GB and a date signifying when the bonus will expire. If you do not see the Enthusiast Bonus, chances are that you did not enter the giveaway and need not to worry about cleaning out space.
In the case that you have more data than allotted on OneDrive after the bonus expires, you will recieve a grace period of 30 days to remove files from your account. In the case that you are unable to do so within the grace period, OneDrive will automatically remove the overage of data randomly (yes, OneDrive will randomly choose files to delete).