It's a DOS based product contained on most of the Brother installation disks. It will also not work under any NTFS operating system ie Windows XP, Windows 2000 etc (unless they were configured FAT32) so unless you're using Windows ME or less, you will probably need to create a DOS boot disk and boot your PC in DOS.
This was how we did this:
1. Install the package (RPCSETUP.EXE)
2. make a DOS boot disk (ie Right Click Floppy Disk Drive & create MS-DOS startup disk)
3. Copy the contents of C:\RPCX to the floppy.
4. Reboot using your DOS disk
5. Now run RPCX and follow the on-screen instructions.<