The leading cause of PNA failures is problems with the PNA Solid State Drive (SSD). These problems are usually preventable (see Preventing PNA SSD Problems), and in many cases, recoverable. The following could save you weeks of downtime and the cost of replacing your PNA SSD.
This document is now on the Keysight PNA Support Website: http://na.support.keysight.com/pna/.
If your PNA does experience a Solid State Drive Drive problem, you will not be able to access this Help file, but you may be able to access the Internet from another computer.