The city government estimated that Migrating from Windows 2000 to a combination of Windows 7 and Microsoft Office 2010 would have cost it a little over 34 million in total. Switching to LiMux, its own Linux distribution, and the OpenOffice.org desktop productivity suite has cost it ???22.8 million, according to a cost comparison published last week that detailed the cost of migrating 11,000 users to open source applications on Linux.