Very simple deal for those with a OneDrive & Dropbox account. Simply click the link, login to your Dropbox account, save the file and your OneDrive account will be credited instantly with the extra 100gb for 1 year.
Thanks to Food on OzBargain(ozbargain.com.au)
If you have your OneDrive/live account registered as a US account you can also stack it with the Bing Rewards 100GB OneDrive valid for 2 years.
http://slickdeals.net/f/7651514-bing-rewards-100-gb-of-free-…
iirc it's still active