When I run my program in the Workbench at the IDL>  command line, it runs fine. When I build my project and create a .sav file, and I click on the .sav file I get an error, ‘Attempt to call undefined function/procedure READ_BMP’. My build does a .RESET_SESSION before building, and it shows a RESOLVE_ALL. The build does not produce any error messages. I checked the value of !path when IDL Workbench first starts, and it includes the folder where the read_bmp.pro file is ( C:\Program Files\ITT\IDL70\lib; ). I checked !path again after running my program, and it still includes this folder. I checked the contents of  my idl.pref file, at C:\Documents and Settings\jane.doe\.idl\itt\pref-10-idl_7_0-windows\idl.pref Besides the comments, this is what it contains (single quotes and ‘+ $’ are mine): ‘IDL_PATH : ;+C:\Documents and Settings\jane.doe\My Documents’  + $ ‘\testidl\Default;+C:\DevIDL\Default;+C:\DevIDLnew\Default’ The problem does not go away if I use MAKE_RT to create a VM executable for my project, when specifying the same problem .sav file. What am I doing wrong?