I think you have to manually upgrade to 2.0 first. Here is my full installation checklist, maybe it helps you:
0. Manually create PFE install folder, place MSVCR71.dll inside, otherwise gacutil.exe will not start. See http://support.microsoft.com/kb/326922
1. Install PFE Deluxe, runs automatically, exit it
2. Extract pfe_accumulative_installer.zip to PFE/Updates
3. Run Install_PFE_Accumulative_Updates.exe to update to 2.15
4. Run ProFlight 2000, exit, run Pro Flight Emulator, exit.
5. Extract AS_PFE_VOICE_PACK.zip to PFE/Updates
6. Run ProFlightEmulator-VoicePack_V100.exe to install the Voice Pack.
7. Run ProFlight 2000, exit, run Pro Flight Emulator and exit it _twice_.
8. Extract PFE_XPack2.zip to PFE/Updates
9. Run PFE_XPack2_Installer.exe to install the Voice Pack 2.
10. Run ProFlight 2000, exit, run Pro Flight Emulator, exit.
11. Extract newcalls.zip to PFE/FS2000/Adv/Wav
12. Run install_newcallsigns.cmd to install missing messages. (only relevant if using original voices)