Fabersky,
the developers of GWX are genius. But evan them can not look in the future. When was GWX3 released? In the very end of year 2008? Any SH3 that is released afterward can go wrong, especialy the "Newer" Download-versions.
What you get may not a System-message but a GWX3-installer-message. The Installer is not very clever; it looks for some files that has to be _not_ in the installed SH3-directory, and only one file that has to be there. So the installer is correct when it states that something is different what it expected.
I would go another way, if i have to. (Which i do not)
First make shure your original SH3 is not installed in "ProgramFiles" and its Directory is read and writeable.
Second, make shure your original SH3 is working.
Use JSGME the first Time if you do not already have. This will create your "MODs"-folder for future needs.
Create new Folder called "_GWX3-Gold" in MODs-folder.
Create new SubFolders "_GWX3-Gold\data\Sound".
Create new txt-file "_GWX3_Gold\data\Sound\P20_@Hedgehog_deepwater.wav "
<== make shure this is renamed to .wav instead of .txt.
Install GWX3 into "_GWX3_Gold".
Delete "_GWX3_Gold\data\Sound\P20_@Hedgehog_deepwater.wav ".
Delete the 5 files related to JSGME (in folder "_GWX3_Gold)".
<== This is an old version, which you will not use!
Delete 2 folders "_GWX3_Gold\MODS\!BACKUP" and ...!INSTLOGS".
Delete file "_GWX3_Gold\MODS\JSGME.ini".
Move all "GWX - "-Mods out of folder "_GWX3-Gold\MODS" into MODs-folder.
Delete folder "_GWX3-Gold\MODS"
Activate "_GWX3_Gold" with JSGME.
Hope this helps.
Some words about post #9 from CaptBones.
If this "Not starting" issue occurs only on the first Start or Doublecklick (the second Start will work) this is a known issue which is related to "GameUX.dll" and its ugly misbehavior.
Greetings.