While SIMATIC WinCC V6.0 SP4 was a landmark release in Siemens' SCADA history, it is important to note that this software was officially discontinued on October 1, 2010. Because it is a legacy product, "new" downloads are typically no longer hosted directly by Siemens for public access.
If you are starting a new project, Siemens recommends moving to their current platforms: wincc 60 sp4 download new