How can I show my own message and then exit setup if the current version of Windows is not supported?

I have to check if the Windows version is not lower than 6.1 which is Windows 7. If it is lower I need to show my own message and then exit setup. If I write this in the [Setup] section:

[Setup]
MinVersion=6.1

the message that is shown is a standard one. How can I show my own message and then exit setup?

Solution

See Handling and customizing errors and messages in Inno Setup.

This particular message is defined by the WindowsVersionNotSupported message.

You can change it in the [Messages] section:

[Messages]
WindowsVersionNotSupported=You are using an ancient version of Windows.