A falling reliability score is a warning signal, not a diagnosis.
Windows Reliability Monitor calculates a System Stability Index. Microsoft documents the index as ranging from 1 (least stable) to 10 (most stable) and says it can help evaluate a computer's reliability. [R1]
The useful question is not:
“How do I raise the score?”
It is:
“Which failures caused the score to fall, and when did they start?”
Use the graph to find when the problem began
Reliability Monitor shows the stability index over time.
Microsoft explains that the graph can help identify the dates when reliability problems began. The accompanying reliability information can then be used to investigate the events associated with that decline. [R2]
A single low number therefore matters less than the pattern.
Look for:
- a sudden drop after a previously stable period;
- repeated drops on several days;
- the same application or component failing again and again;
- failures beginning immediately after a driver, update, or software change.
The date of the drop is a starting point for diagnosis, not proof that the most recent change caused the problem.
Look at the events underneath the score
Windows keeps reliability records that are derived from the Windows Event Log.
Microsoft documents the Win32_ReliabilityRecords data as containing information such as the event identifier, message, source name, product name, and the time the event occurred. [R3]
Those records are more useful diagnostically than the score alone.
For example, a falling index may coincide with repeated application crashes, operating-system failures, hardware-related events, or another recurring fault. Investigate the repeated event itself instead of trying to repair the index.
Compare failures with recent changes
One of Reliability Monitor's strengths is that it places system changes next to failures.
Microsoft describes using changes such as application installation or removal, operating-system updates, and driver additions or modifications alongside application failures, operating-system crashes, and hardware failures. [R2]
That timeline can reveal useful relationships.
For example:
driver update → repeated application failure → falling stability index
is more informative than:
stability index = 4
But timing is still not proof of cause. A change that happened before a failure is a hypothesis to test, not something to undo automatically.
Do not chase every isolated event
A reliability record can describe a real failure without meaning the entire PC is unhealthy.
Focus first on repeated failures, user-visible problems, or several related events occurring together.
If one application crashed once and never fails again, that is very different from the same process failing several times per day.
Likewise, do not reinstall drivers, reset Windows, or remove recent updates only because the score moved downward. Those actions should follow evidence from the underlying events.
How do I open Reliability Monitor?
Microsoft documents the perfmon /rel command as opening Reliability Monitor directly. [R4]
You can also search Windows for View reliability history.
Select a date where the graph falls and inspect the events shown for that period. Record the application, component, event time, and any error details before making changes.
What should I do now?
- Open Reliability Monitor and look at the trend rather than only today's score.
- Identify the date where stability first dropped noticeably.
- Inspect the reliability events shown on that date and the days around it.
- Look for the same application, Windows component, or hardware-related event appearing repeatedly.
- Compare those failures with recent application installs, Windows updates, and driver changes.
- Treat timing as a clue, not proof that the newest change caused the failure.
- Investigate the repeated underlying event rather than trying to “repair” the stability index itself.
- If the index falls because of repeated crashes, unexpected shutdowns, or hardware-related events, follow the diagnostic path for those specific failures.
The goal is not to make the graph look better. The goal is to use the graph to find which failures are recurring and when they began.