Extend Volume is greyed out medium
Right-click on a drive in Disk Management → "Extend Volume" is greyed out / disabled.
Cannot shrink volume / Shrink is greyed out medium
Right-click in Disk Management → "Shrink Volume" is greyed out, or the maximum shrink amount is much less than expected.
Disk shows as "Not Initialized" low
New disk appears in Disk Management with the label "Not Initialized" and all space shows as unallocated.
Disk Management won't open or crashes high
Typing diskmgmt.msc shows an error, the window opens and immediately closes, or the snap-in fails to load.
No unallocated space visible medium
You want to create a new partition but there is no unallocated (black) space visible in Disk Management.
Drive letter is missing or changed after reboot low
A drive partition that was accessible (e.g., E:) is now missing a letter, or has a different letter after restarting Windows.
Access Denied when opening a partition high
Double-clicking a drive shows "Access Denied" or "You don't currently have permission to access this folder."
Disk Management shows wrong disk size medium
A 2 TB drive shows only 746 GB, or a 500 GB SSD shows as 465 GB, or a drive shows significantly less than its marketed size.