How can I merge unallocated space back into my D drive?

You can use Diskpart to delete any partitions that are standing between your D drive and the unallocated space. But be super careful! Check that you’re deleting the right partition because once it's gone, there’s no coming back. After that, you should be able to extend your D drive easily. If you're unsure, you can follow this guide on using Diskpart for help: (Insert guide link here). Just make sure you’ve backed up everything important.

Windows can be picky about partitioning. If there’s anything in between your D drive and the unallocated space, it won’t let you merge them without deleting or moving that partition. I recommend using a third-party partition management tool because Disk Management often has these limitations. Also, check if the partition you’re trying to remove is crucial for system boot; you might want to disconnect the D drive first to ensure your system runs fine without it.

Before you can extend your D drive, make sure that the unallocated space is directly next to it on the drive. If there are any partitions in between, Windows won’t let you expand it. You might need a tool like Gparted to move or delete those partitions if they are blocking the space. Just keep back up your data before making any major changes!