If you intend to transfer your Dark Souls: Prepare to Die Edition save data from Games For Windows Live to Steamworks, you have until February 16th.
After that date, Bandai Namco say you won’t be able to transfer your saves over any longer. You can find instructions on how to perform the transfer here.
In recent months, Bandai Namco have increased their PC output significantly. The company has been bringing its Naruto games to PC and will release Dragon Ball Xenoverse on PC as well.