Windows Has a Hidden Tool That Can Diagnose Your PC in 60 Seconds

Windows Has a Hidden Performance Diagnostic Tool — Here’s How to Use It

If your Windows PC suddenly feels slow, the usual reaction is to open Task Manager, stare at CPU and memory percentages, and start closing applications one by one.

But what if Windows could perform a more structured diagnostic check for you?

It can.

Built into Windows is Performance Monitor, a long-standing administrative and troubleshooting utility that can generate a System Diagnostics report with the command:

perfmon /report

Microsoft documents /report as the option that starts the System Diagnostics Data Collector Set and displays a report of the results. The command is available in Windows 10 and Windows 11, as well as several Windows Server versions.

And the best part?

You don’t need to install third-party diagnostic software.

What Is perfmon /report?

perfmon is short for Performance Monitor.

It is one of those Windows utilities that has been around for years but doesn’t receive much attention from everyday users. For IT professionals, however, Performance Monitor can be useful for investigating system performance and troubleshooting problems.

When you run:

perfmon /report

Windows launches its System Diagnostics data collection process and generates a report containing information about the current state and performance of the computer.

Microsoft itself recommends generating a System Diagnostics report with perfmon /report as part of troubleshooting certain Windows performance and freezing problems.

This makes it particularly useful when you’re trying to answer a simple but important question:

What is actually making this computer slow?

How to Run the Windows System Diagnostics Report

The process is straightforward.

Step 1: Open PowerShell as Administrator

Right-click the Start button.

Select:

Terminal (Admin) or PowerShell (Admin), depending on your version and configuration of Windows.

You may receive a User Account Control prompt. Select Yes.

Step 2: Run the command

Enter:

perfmon /report

Then press Enter.

Windows will begin collecting diagnostic information.

The collection period is typically around a minute, although the entire process can take longer depending on the system.

Don’t close the window simply because the report isn’t displayed immediately.

If the command appears to take longer than expected, give Windows additional time to complete the diagnostic process.

Step 3: Review the report

Once the process finishes, Windows opens the System Diagnostics Report.

This is where the command becomes particularly useful.

Instead of looking at one percentage in Task Manager, you get a broader view of the system’s health and performance.

What Does the Report Tell You?

The report can provide information across several areas of your computer.

Depending on the system and issues detected, you may see warnings related to hardware, drivers, services, security configuration, system performance and resource utilization.

One of the most useful aspects is that the report organizes findings into categories so that you can investigate potential problems rather than simply guessing.

1. Warnings and Diagnostic Findings

The report can highlight issues that deserve attention.

For example, you may encounter warnings involving:

• Hardware devices
• Drivers
• System configuration
• Security-related settings
• Windows services
• Performance problems
• Resource utilization

A warning doesn’t automatically mean that your computer is broken.

That’s important.

A diagnostic report identifies conditions that may deserve investigation. You still need to determine whether a particular warning is relevant to the problem you’re experiencing.

2. CPU, Memory, Disk and Network Activity

Performance problems can originate from completely different parts of a system.

A computer with plenty of RAM can still feel slow because of disk activity.

A computer with a fast SSD can still struggle because of CPU-intensive applications.

A machine with a powerful processor can still experience delays because of memory pressure or network-related activity.

The diagnostics report provides information that can help you investigate these different resources.

This is where the tool becomes useful for IT troubleshooting.

Rather than saying:

“The computer feels slow.”

You can start asking:

“Is CPU utilization unusually high?”

“Is disk activity causing the slowdown?”

“Is memory under pressure?”

“Is a particular process responsible?”

That shift — from guessing to measuring — is one of the most important habits in IT support.

Finding the Processes Consuming Resources

Another useful part of Windows performance diagnostics is identifying processes associated with high resource usage.

If an application is consuming significant CPU, memory or disk resources during the diagnostic period, that information can help narrow down the investigation.

For example, imagine someone tells you:

“My computer becomes extremely slow whenever I open this application.”

Instead of immediately reinstalling Windows, you can collect performance information while reproducing the problem.

You may discover that a particular process is consuming unusually high CPU or generating substantial disk activity.

That gives you a much better starting point.

The Important Limitation: It’s a Snapshot, Not a Crystal Ball

There is one important point that shouldn’t be overlooked.

perfmon /report is not a magical tool that permanently monitors everything your computer does.

It collects information during its diagnostic run.

That means timing matters.

If your computer becomes slow only when you launch a particular application, generate the report while the problem is occurring or immediately after reproducing it.

Otherwise, the diagnostic window might not capture the behavior you’re trying to investigate.

For persistent or intermittent problems, Windows also provides Performance Monitor functionality for collecting performance-counter and event data over longer periods. Microsoft documents Performance Monitor as a tool for examining how programs affect computer performance and for collecting performance logs.

The Bonus Command: perfmon /res

There is another useful command worth remembering:

perfmon /res

According to Microsoft, /res starts Resource View, commonly known as Resource Monitor.

Resource Monitor takes the resource-monitoring concept much further than a basic Task Manager glance.

You can investigate:

• CPU activity
• Memory usage
• Disk activity
• Network activity
• Processes
• Services
• Network connections
• Files being accessed

This can be extremely useful when troubleshooting a computer that is behaving strangely.

For example, if disk usage suddenly reaches 100%, Resource Monitor can help you investigate which processes are generating the activity and what files are involved.

If network traffic suddenly increases, you can investigate the processes and connections associated with that activity.

perfmon /report vs perfmon /res

Think of the two commands this way:

Microsoft officially documents all four switches.

That gives you a surprisingly capable troubleshooting toolkit without downloading anything.

Why This Matters If You’re Working in IT

If you’re trying to build a career in IT, tools like Performance Monitor are worth learning.

Being an IT professional isn’t simply about knowing how to restart a computer, install software or replace hardware.

A good technician learns to diagnose before making changes.

Consider this scenario.

A user tells you:

“My computer is slow.”

You could immediately start deleting files, disabling startup applications and uninstalling software.

Or you could approach the problem systematically:

1. Reproduce the problem.
2. Collect performance data.
3. Identify the affected resource.
4. Identify the process responsible.
5. Investigate the underlying cause.
6. Apply an appropriate fix.
7. Test the system again.
8. Document what you discovered.

That is a much more professional troubleshooting workflow.

And when you can show your manager a diagnostic report rather than simply saying “I think the computer is slow because of RAM,” your recommendation becomes much easier to evaluate.

A Practical IT Troubleshooting Scenario

Imagine you’re supporting an employee whose Windows laptop has become extremely slow.

They have 16 GB of RAM, an SSD and a relatively modern processor.

Task Manager shows that the CPU isn’t consistently maxed out.

Instead of immediately recommending a hardware upgrade, you run:

perfmon /report

The diagnostic report gives you additional information to investigate.

You then open:

perfmon /res

While reproducing the problem, you monitor CPU, memory, disk and network activity.

You discover that a particular process is generating unusually high disk activity.

Now you have a lead.

You can investigate:

• What application owns the process?
• Is it expected behavior?
• Is the application updating or indexing files?
• Is there a service associated with it?
• Is the process behaving abnormally?
• Is there an application update available?
• Is the storage device experiencing problems?

That’s considerably better than randomly changing settings.

Don’t Confuse Diagnostics With a Guaranteed Fix

It’s also important to manage expectations.

The System Diagnostics report doesn’t automatically fix every performance problem.

It is primarily a diagnostic and investigative tool.

A warning doesn’t necessarily mean that you should immediately disable a service, replace a component or change a configuration.

Treat the report as evidence.

Investigate the finding, understand its context and then decide what action — if any — is appropriate.

This distinction is particularly important for people learning IT support because aggressive troubleshooting can sometimes create more problems than it solves.

A Small Command Worth Remembering

If you work with Windows systems, add these commands to your personal troubleshooting toolkit:

perfmon /report

for a System Diagnostics report, and:

perfmon /res

for Resource Monitor.

Microsoft officially documents both commands, and its troubleshooting guidance specifically recommends perfmon /report for generating a System Diagnostics report when investigating Windows performance and freezing issues.

You don’t need another “PC cleaner.”

You don’t need to immediately download a third-party optimizer.

And you certainly shouldn’t start changing random system settings just because a computer feels slow.

Measure first. Diagnose second. Fix third.

That’s one of the fundamentals of professional IT troubleshooting.

Final Thoughts

Windows contains a surprising number of administrative and diagnostic tools that many everyday users never encounter.

Performance Monitor is one of them.

The next time someone tells you, “This computer is slow,” don’t immediately start guessing.

Open an elevated PowerShell or Terminal window and try:

perfmon /report

Then, when you need a closer look at what’s happening in real time:

perfmon /res

These aren’t magic commands — and they won’t replace proper troubleshooting — but they can give you significantly more evidence to work with.

For anyone entering IT, that’s an important lesson:

Good troubleshooting isn’t about guessing the fastest. It’s about finding the evidence.