When you say you applied the 4GB patch, I'm assuming you mean that you applied the patch to the SH3.exe file that will allow it to make use of more RAM than the 2GB (?) to which it was initially limited.
However I don't think you've said whether you are running the 32-bit or 64-bit version of Windows.
If you are running the 32-bit version, it will not matter how much RAM you have installed or how much RAM the SH3.exe will be able to use - the OS itself cannot recognize more than 4GB max. Using the 3GB switch in the boot.ini file may help make more RAM available for games and other applications, but AFAIK you haven't said whether or not you are using it.
If you are running the 64-bit version your OS can recognize and use more RAM provided you have it installed, and if you do have more RAM the game should be able to use a decent chunk of it once it's been patched for that purpose.
In either case I would advise that you disable all mods and try at first to run the game without any additional modifications, if you have not done so already, to see if the same CTD occurs.
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