Error Code 4120: Failed to Adjust Partition Size

Solution to invalid parameter or information code 4120 occurring when you clone from a large drive to a smaller drive with AOMEI Backupper.

By @AOMEI
Last Updated November 13, 2025

This article applies to: AOMEI Backupper all versions.

Introduction

Sometimes, when you clone from a large drive to a smaller drive, you may encounter error code 4120:

Clone is initializing...

Checking volumes...

System cloning...

Information Code: 4120

Failed to adjust partition size.

Solutions

Method 1: Delete all partitions on target drive and clone again

Press Windows + X and select Disk Management. Right-click on each partition on the target drive and select Delete Volume.

After the target drive shows unallocated space, open AOMEI Backupper and try disk clone again.

Method 2: Edit the partition size manually

Before starting clone, click Edit Partitions > Manually adjust partition size to edit the size of each partition manually.

If there is still any problem, please feel free to contact us.