Reliability Index Score
Reliability Monitor is an advanced tool that measures hardware and software problems and other changes to your computer. It collects 24 hours of data before it displays any results and calculates the stability index that ranges from 1 (the least stable) to 10 (the most stable). You can use the index to help evaluate the reliability of your computer by reviewing the reported application failures, Windows 7 failures, Miscellaneous failures, Warnings, and Information. Any change you make to your computer or problem that occurs on your computer affects the stability index.
In Action Center> Maintenence> View System History comes up a window of a Reliability Score!