In less than a year, Tabs3/PracticeMaster versions 15.1 and 15.2 will no longer be supported. Support for those versions ends on June 1, 2015. Support for version 15.3 will continue until June 1, 2016.
If you use these older versions, you will need to update in order to receive support after June 1 of next year. Tabs3/PracticeMaster stopped selling version 15.2 in January 2010, so it will have been supported for more than five years. For more details, see the Knowledge Base article here.