I found out some really interesting things about the game files. Maybe you have already wondered why the CD version is more than 120 MB bigger than the disc version? As with all Microprose adventure games, the speech data is packed in SPEECH.HAG, but this file is only about 27 MB big. If you compare the other files, you'll notice that GLOBAL.HAG is 100 MB bigger on the CD version than on the disc version. But since the only difference between both versions is the speech, there seems to be no sensible reason for that.
I did some research and found some documentation of the HAG format. HAG files can be compared to ZIP archives as they are a package of multiple files, but use an internal packaging algorithm. When I unpacked GLOBAL.HAG from the CD version, I found out that it contains a file called 00GRUNT which is exactly 100,000,000 Bytes in size and just contains useless junk data, just for the reason to make the CD version bigger and to make it unrealistic to copy it on multiple floppy discs (which was an appropriate copy protection when the game was released).
After some effort, I was able to remove the unnecessary 00GRUNT from GLOBAL.HAG and repacked the rest of the originally included files.
This means that if you use my modified GLOBAL.HAG, you can reduce the game's size by 100 MB without removing anything important! I have tested it and the game did indeed work without any problems. If you want to try it for yourself,
download GLOBAL.HAG from my server and extract it to the RESOURCE folder of Return of the Phantom, replacing the existing file. It is adviseable to replace
GLOBAL.IDX also, but this is not required as long as the file PHANTOM.RTN exists.
(If an admin reads this, I recommend to exchange the files on the download archive, as this will save you a lot of traffic)
You can also use this file to remove the copy protection question from the disc version, which might be another reason why they "protected" the GLOBAL.HAG file on the CD version.