I've finally gotten around to re-downloading, uninstalling, and re-installing the GOG version of the game in order to repeat my data file comparison that I had previously performed to shed some light on the issues people were having with missing textures/models/etc.
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<span class="podkreslenie">From the earlier thread...</span>:
Missing:
xp1patch.bif (7.69MB): I'm not sure this file is used anymore. The 1.69 linux server patch specifically instructs you to delete this file.
Incorrect File Size/Date:
xp2patch.bif (127,609kb): Critical rebuild patches this file to a 359,896kb file that was modified 3 years after the GOG install file (4/29/2005 vs. 5/15/2008)
xp3.bif (463,718kb): Critical rebuild patches this file to a 627,919kb file that was modified 9 hours before the GOG install file (5/15/2008 10:46PM vs. 1:46PM). Weird.
Given the above file sizes, there's your missing ~0.4GB
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With the latest GOG version of the game, the above mentioned file size issues have been corrected; the critical rebuild patch should no longer be necessary.
The xp1patch.bif file is still missing, but I am fairly certain that file is unnecessary given the above reference to it needing to be deleted for running a Linux server, in addition to it not appearing to contain any new content (just curious looking res* references that I do not know the nature of) when you look at what it contains.