You will need to manually set QTDIR and add the \bin directory to your system PATH to run the tools like qmake . Modern Recommendations
Today, Qt 3 is long-retired legacy software, but if you must download it for maintenance or porting old code, here is how you can find it. qt 3 download windows
Because there was no official free Windows release, you won't find a standard .exe installer on the modern Qt website . You have two main options: You will need to manually set QTDIR and