If you know how to create an installer using NSIS, you'll probably want to know how to create the uninstaller too :)
So you have to write a section named "Uninstall" inside your .nsi script file.
Delete "$DESKTOPYour Application.lnk"
RMDir /r "$SMPROGRAMSYourApp"
RMDir /r "$INSTDIR"
Sometimes you may want to embed some other installer in your installer. As an example if you need Java as a prerequisite then you can embed Java installation inside your installer. Then it will run the Java installation before installing your application, when you run your installer.
So let's write a section to embed JRE installer in your installer
Section "jre" SECJRE
While writing my installer I wanted to install JRE (embed JRE installer in my installer) only if Java is not installed already. So I had to detect whether Java is already installed.
My previous post on NSIS points to a quick start guide (in Harshani