Microsoft loves giving away free OneDrive space. After gifting 100GB of free storage last week for signing up to Bing Rewards, the software maker has a similar offer aimed at Dropbox users today. If you’re an existing Dropbox user then all you have to do is sign in to your account to obtain 100GB of free OneDrive storage for a year. It’s not the two years from the Bing Rewards program (which you can still claim today), but it’s enough if you’re even considering switching to Microsoft’s cloud storage. While it's not clear if this offer is time limited, it's probably worth claiming the 100GB storage now just in case this is a temporary promotion.