I am having the same problem, installing with Big World Setup, game installed via the Beamdog Client. I have all three games, and they are not installed on the home drive. Also somewhere in the installation it deletes the Siege of Dragonspear executable, so I have to reinstall it everytime I want to retry install the mods. Can anyone help?
##### Enhanced Edition Trilogy #####
### 0000: Enhanced Edition Trilogy ###
Ready for installation
Setup-EET.exe --no-exit-pause --noautoupdate --language 0 --skip-at-view --args-list p "G:\BeamDog\00806" --force-install-list 0 --logapp
[setup-EET.exe] WeiDU version 24200
Using Language [English]
Using .\lang\en_us\dialog.tlk
Installing [EET core - resource importation] [1.0 RC9.2]
INTERACTIVE = 1
LANGUAGE = en_US
argv[0] = p
argv[1] = G:\BeamDog\00806
Copying and patching 1 file ...
LANGUAGE_BG2 = en_US
Creating 1 directory
Copying 1 file ...
Copying 1 file ...
G:\BeamDog\00783>ECHO AMD64 | FINDSTR AMD64 1>NUL && SET arch_var=AMD64 || SET arch_var=x86
G:\BeamDog\00783>ECHO AMD64 1>EET\temp\arch_var.txt
arch_var = x86_64\
Copying and patching 2 files ...
G:\BeamDog\00806 directory assigned via auto install batch command
Enter the full path to your BG:EE+SoD installation then press Enter.
Example: C:\Program Files (x86)\BeamDog\Games\00806
Invalid directory, or incorrect BG:EE+SoD installation.
It is safe to abort this installation by closing this window or pressing Ctrl+C.