Windows 11 PC slow or disk at 100%? What to check first

By Saadat Rafiq · 2 min read · 9 steps · Published 6 October 2026

Device

Windows

Shown on

Windows 11 Enterprise 25H2 (build 26200.9457), Microsoft Cloud PC

App

Settings

Path

Settings › System › Storage

Real screenshots

8 of 9 steps

Checked

October 2026

Sources

2 official, linked below

Step by step

1. 

   Open Task Manager and sort by Disk

   Press Ctrl + Shift + Esc. On the Processes page, click the Disk heading so the busiest app is at the top. Do the same with CPU and Memory. The percentage above each column is the total.

   Done

2. 

   Look at the top rows

   An app that stays at the top for several minutes is the cause. Close it, or update or remove it. Our Cloud PC was idle, with disk use at 3%.

   Done

3. 

   Open Startup apps

   Click Startup apps on the left of Task Manager. Status shows whether each app starts with Windows, and Startup impact how much it slows the start.

   Done

4. 

   Disable what you do not need

   Select an app and click Disable at the top, or right-click it and choose Disable. It still works when you open it yourself.

   Done

5. 

   Or use Settings

   The same list is in Settings, Apps, Startup, with a switch for each app.

   Done

6. 

   Free up disk space

   Open Settings, System, Storage. Click Temporary files and remove what you do not need, or switch on Storage Sense. Our drive had 86.1 GB free.

   Done

7. 

   Install updates

   Open Settings, Windows Update and click Check for updates. Microsoft also points to Advanced options, Optional updates for newer drivers.

   Done

8. 

   Run a quick virus scan

   Malware can keep the disk and processor busy. In Windows Security, Virus & threat protection, click Quick scan.

   Done

9. Restart

   A restart closes everything that piled up and finishes pending updates. Use Restart, not Shut down.

   Done

About this guide

A slow PC usually has one busy app, too many apps starting with Windows, a nearly full drive or a pending update. Task Manager shows the first two in a minute. The order below follows Microsoft's tips for PC performance, starting with what you can see.

The screenshots are our own, taken on Windows 11 Enterprise 25H2 (build 26200.9457) running as a Microsoft Cloud PC, a Windows PC that runs in the cloud. The Settings app is the same on Home and Pro PCs; where the Cloud PC shows something different, the step says so.

Good to know

If one Windows process such as Service Host is at the top for a long time right after an update, let the PC finish: updates often work in the background for a while.

More power for plugged-in PCs: how to change the power mode on Windows 11. Full virus scan options: how to scan a Windows 11 PC for viruses with Windows Security.

In short: Ctrl + Shift + Esc, sort by Disk and CPU. Startup apps: disable what you do not need. Settings, System, Storage: free space. Install updates, Quick scan, restart.