If you have an older copy of the original VDL 2.5 DVD (before library version 2.5.5 came out in 2012) that 2.5.0 DVD shipped with a Vise installer. If you attempt to run the installer, you'll find that it spins for a bit, then just quits. This installer does not work on Macintosh operating systems greater than 10.5+ (Leopard+).
Instead, we recommend getting a 2.5.5 Library Replacement (available as a direct download, or as a physical DVD-ROM). This will include the most current version of the VDL library and it uses a more robust and efficient version of the Native Instruments Kontakt Player. The older, pre-2.5.5 library is not recommended on modern operating systems.