FileInfo.com - The File Extensions Resource

.FP4 File Extension

File Type	FileMaker Pro 4 Database
File Format	File
Common?	No
File Description	Database created by FileMaker Pro 4; stores data in a proprietary FileMaker database format; version 4.0 was developed by Claris Corporation, while version 4.1 was released by FileMaker, Inc.
Program(s) that open fp4 files	Mac / Windows: FileMaker Pro 4 or later

Information from FileInfo.com - The File Extensions Resource.
http://www.fileinfo.com/extension/fp4