Windows 11 disk usage 100% even with no apps open, very laggy

Use the resource monitor to what app is doing all the disk IO.  Replace your drive with an SSD if you haven't done so already.

   Maybe it's doing windows updates.  I no longer shut down my machine when I'm done using it so it's always ready to do work for ME when I sit in front of it.

Hey, yeah that’s super annoying 😅

So basically your disk goes 100% right after boot even when nothing’s open, and system becomes laggy… I faced something similar on my old Windows 11 setup, turned out it wasn’t just one thing.

What worked for me:

check Task Manager → sort by disk, sometimes “System” or Windows Update runs heavy in background

try disabling Windows Search indexing (this one helped me a lot honestly)

also check startup apps, some hidden stuff loads silently after boot

Not sure if it helps but sometimes it’s just Windows doing background tasks for few mins after startup.

I ran into this while setting up systems for YOUR BRAND NAME.

Does the usage stay 100% forever or settle down after some time?

Disable the SysMain and Windows Search services in Services Manager, and run the chkdsk /f /r command to check for disk errors.

Hello,

Try temporarily disabling SysMain and Connected User Experiences and Telemetry services, see if that helps.

If your device has StorAHCI.sys driver, you can attempt to try Message Signaled Interrupt (MSI) mode disabled. This could significantly reduce disk usage.

Additionally, see if other suggestions in this fix helps you:

https://www.kapilarya.com/fix-100-disk-usage-in-windows-11

Let us know if this helps!

Note: Included link in this reply refers to blog by a trusted Microsoft MVP.