Use Reliability Monitor to determine if a software installation has negatively affected your system’s stability. Systems that do not experience failures are considered stable by the Reliable Monitor and hence, it rates them with a score of 10. On the other hand, a low score or zero indicates that your system is undergoing a period of instability due to failures or forced reboots. The Reliability Monitor does not differentiate between valid reboots such as, installing a service pack or reboots caused by faults, however, the monitor chart will help you understand both situations.
The Stability chart displays a graph of the stability score (index) on a daily basis. Days are divided into columns which may include warning, info and/or error icons to indicate events. Such events are further detailed in the lower part of the Reliability Monitor window.
The Stability measurement (stability index) is based on data collected over the lifetime of a system. However, the utility maintains a history of 1 year. The index is calculated from the number of failures that occurred over the preceding 28 days. Hence, it needs 28 days of data before establishing a valid baseline, otherwise the index line on the graph is dotted. Recent failures have more weight on the index value than past ones. You can see that the stability index ascends to a max value over time when no system failures are encountered and drops heavily when a failure occurs.