Patch 1.1 fixes several bugs. Most digital distribution versions already include this patch.
%USERPROFILE%\Documents\GTA3 User Files
Ensure Data Execution Prevention (DEP) is set to the default (Windows programs and services only).
OpenRW is an open source game engine that attempts to re-implement the engine used in classic GTA 3, Vice City and San Andreas in order to ensure a better compatibility with modern system and playable in the future. It currently supports only GTA 3 and it is currently not finished yet, however you can still play the game with it. Bear in mind that you need to compile it from its source code, instructions and requirements are available