AstralWanderer: It isn't a 32/64-bit issue - the headers of the nexus.exe and nexusDX9.exe files have values set to block them running on WinXP/Win2K (causing them to fail with the "not a valid Win32 application" message). Given that Nexus originally ran on Win9x plus the GOG gamecard still lists it as WinXP compatible, this does need to be addressed by GOG Support.

In the meantime however, affected owners can get the files to run on WinXP (and Win2K) with the following steps:

* Download and install a hex editor (I suggest using the free HxD);
* Make backup copies of nexus.exe and nexusDX9.exe (HxD will make backup copies too, but better to play safe);
* Open nexus.exe using HxD and change bytes 140 and 148 (hex) from 06 to 04 (see the outlined values in Nexus.gif) - save this altered file;
* Open nexusDX9.exe using HxD and change bytes 180 and 188 (hex) from 06 to 04 (see the outlined values in NexusDX9.gif) - save this altered file;
* Try running either file, both should now work.

I have tested this with multiple savegames from different parts of the campaign and encountered no problems (on a WinXP SP3 system) though I can't guarantee that this will work for everyone else. However my experience seems to show there is no valid reason to block execution on WinXP and this is likely due to Mithis using Visual Studio 2015 or a similar tool that requires patching for WinXP support.

abr_alex: Any news on the issue investigation?