AutoCAD LT does not have the NETLOAD command which is needed to load the hotfix DLL file, which means the DGNPURGE command is not usable within AutoCAD LT. However, AutoCAD LT 2015 has the enhanced PURGE functionality, so it is recommended to use version 2015 to purge files. As an alternative to the hotfix, converting a DWG file to DXF and then back again, or to DGN and back, or using WBLOCK to write a new file has the potential to remove unwanted DGN elements.