The parallel port driver is only needed when you have @ltium's Nano Board system installed. You don't need it for any other function.
As to why you are getting the error - there are several possibilities. If you had a previous version installed, and the driver is still on the system, it may be read-only. The installer may not be able to install the new driver because it can't erase, or overwrite, the old one. Another possibility is you may have experienced a one-time installer error. You could uninstall, and try again. Does your system even have a parallel port? Some newer computers only have USB