By "encrypted," do you mean it has an owner name or do you mean that when you open it in a text editor, it looks strange?
Btrieve data files require the Btrieve / Pervasive PSQL engine in order to be read. Once you have the engine, you can open it and read it. You'll still need to know the record layout (or guess) in order to extract meaningful data from it. Btrieve files do not store field metadata so any Btrieve tool will only see the record as a collection of bytes.
If you know the record structure, you can create a table definition using DDF Builder or the Pervasive Control Center, and then access the table using ODBC (or JDBC, ADO.NET, PDAC, ActiveX, or OLEDB) and extract the data using your favorite tool.