Press Ctrl + Shift + Esc, open Processes in Task Manager, and sort by Disk. A brief spike while copying files or installing updates can be normal. If the PC stays slow after the work ends, check which drive is busy and what process keeps using it.
01Check activity and free space separately
Section linkIn Task Manager, go to Performance and select the affected disk. Active time shows how busy the drive is; it does not tell you how much space is left. Check free space separately in Settings → System → Storage. A drive with plenty of space can still be busy, and deleting files is not a fix for every spike.
02Match the slowdown to what the PC is doing
Section linkIf a file copy, update or sync is running, let it finish and check the same disk again. If a familiar app keeps topping the Disk column, save your work and quit the app normally. Reopen it and see whether the slowdown returns. Leave unfamiliar system processes alone. If it happens only after sign-in, check Startup apps in Task Manager for a nonessential app you recognize and test with it disabled.
03If the disk stays busy after restarting
Section linkRestart, let startup activity settle, and check the disk again before reopening apps. Note the drive, the process at the top and whether apps still freeze. If you suspect malware, use a Quick scan in Windows Security under Virus & threat protection. Avoid changing several services at once; it makes the cause harder to identify.
04Back up if Windows reports a drive warning
Section linkOpen Settings → System → Storage → Advanced storage settings → Disks & volumes and view Properties for the affected drive. If Windows reports a critical storage warning, back up important files to another device or location and contact support. Windows’ built-in critical health monitoring applies to NVMe SSDs, so no alert does not rule out trouble on a SATA SSD or hard disk.