We use a nsis installerscript. You can find it in src/ports/win32/.
You can use the Windows version of nsis or the linux version (makensis) to build the installer.
There is also a makefile target named
win32installer - so you can type
make win32installer to build the installer (if you have nsis installed).
The maps are automatically compiled, the languages are automatically updated and the pk3 files are build, too. All you have to do is to place the windows binaries in the right places (everything to the game root - except the game.dll which goes into the base/ dir).