I have a 2TB HDD, and there was a problem during setup. Thus, the HDD was set up with two 1TB partitions. I shrunk Part 2 to make it smaller, but the option was greyed out when I tried to add it to Part 1.
Reducing the partition number on your hard drive is beneficial, especially when they are redundant. However, the Windows Disk Management tool has too many limitations on the partition resize process, including specific file systems and adjacent unallocated space.
Moreover, you cannot merge two partitions on the Disk Management unless you delete one as unallocated space. Then, you can use the unallocated space to extend the partition. Sounds complicated to computer beginners. Thus, I will introduce a simpler third-party software as the alternative: EaseUS Partition Master. This tool can help you merge two successive partitions or extend one partition with non-adjacent free space.
Learn how to merge two adjacent partitions with EaseUS Partition Master:
Step 1. Locate the disk in Partition Manager, right-click on the partition that will last, and select "Merge."
Step 2. Choose the partition behind it to combine. Click "OK" to set up.
Step 3. Click the "Execute Task" > "Apply" to combine two adjacent partitions.
If you want to shrink the partition to create unallocated space and expand it next time, try using the "Allocate Space" of EaseUS Partition Master instead of deleting it via Disk Management.
More Information: Combine Partitions By Allocating Space
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