Hi SimonKob,
Here is the link to the current versions of VISA. You will have to have VISA installed on your development machine before you can create an installer for it.
Click on the "Additional Installers" category when creating your application installer in the LabVIEW 8 project. Click on the checkbox for NI-VISA runtime. When you build the application installer, it should include the VISA runtime engine installer. Hope this helps!
Regards,
Missy S.
Project Engineer
RoviSys