I can confirm the rolling conversation on this topic, and also confirm that I know of no way to take a standalone FPS Creator game that has been encrypted and compressed into a single executable, and then extract the map level files to recover them. When the different files are compressed into a single executable, they are almost impossible to separate. I have no objections to methods being discussed here which can recover files from an executable you created yourself. Naturally, if your purpose is to extract files from other games in order to obtain and illegally use the assets, then that's a separate matter.
I can also add that if the game you have is indeed separated into a core executable and then a Files folder containing the various assets, the FPM files contained in the mapbank folder can be accessed freely, by following these steps:
1. Take an FPM file and rename the file extension to .ZIP
2. Open this renamed ZIP file with WinZip/WinRAR and enter the password 'mypassword'
3. Extract the files into a new folder so you can access the individual files (header info, entity database, etc)
4. From these files you can reconstruct a new ZIP with any modifications you want to make
5. When you create the ZIP from the above modified files, ensure the zip holds the files in its root folder, not a subfolder
6. When the ZIP is created, do so with the password 'mypassword'
7. Rename the ZIP file back to a .FPM file extension
You can then load the FPM file back into FPS Creator as normal, and it will contain the original and modified files you had access to above.
The real lesson, of course, is to save early and save often, and ensure you have three tiers of backup systems in place to ensure you never lose work. Redoing something over again might improve the end result, but can be awful tedious if the work to be recreated took weeks instead of hours. Hope the above tip helps in some way!
Hogging the awesome since 1999