Disk Partitions: How to Extend C: Without Losing Data
In this guide
Is your C: drive full while D: is almost empty? Want to split a new drive into two parts, one for Windows and one for your files? Windows can only do some of this. In this guide we explain in simple terms what partitions are, when it’s worth changing them, and how to extend C: without losing data using AOMEI Partition Assistant.
The short version
- A partition is a “slice” of the drive that Windows sees as a separate drive (C:, D:…).
- Windows Disk Management can only extend C: if the free space is right after it, which rarely happens.
- With AOMEI Partition Assistant Pro or EaseUS Partition Master Pro you move space from D: to C: in a few clicks, without deleting anything.
What partitions are (in simple terms)
Think of the drive as a wardrobe: the partitions are the shelves. Windows (C:) sits on one shelf, your files (D:) on another. If the Windows shelf fills up, the PC slows down and updates fail, even if the wardrobe still has plenty of free space. Changing partitions means moving the shelves without emptying the wardrobe.
What you can do (and what Windows can do)
| Task | Disk Management (Windows) | AOMEI / EaseUS Pro |
|---|---|---|
| Shrink a partition | Yes | Yes |
| Extend C: with non-adjacent space | No | Yes |
| Move space from D: to C: directly | No | Yes |
| Merge two partitions without losing data | No | Yes |
| Convert MBR ↔ GPT without deleting | No | Yes |
| Migrate Windows to a new SSD | No | Yes |
See AOMEI Partition Assistant Pro
See EaseUS Partition Master Pro
Both are lifetime licences for 2 PCs and handle the same main tasks: pick whichever interface you prefer.
Guide: extend C: by taking space from D:
With the Allocate Free Space feature in AOMEI Partition Assistant, you move space from one partition to another in a single operation. The screens are simplified: names may differ slightly.
Make a backup and open the program
The operations are safe, but a backup of your important files is always a good idea. Then open AOMEI Partition Assistant: you’ll see the PC’s drives and partitions.
Right-click the D: partition
Choose “Allocate Free Space”
In the D: partition menu you’ll find Allocate Free Space: it’s made exactly for giving space from D: to another partition.
Click Allocate Free Space
Decide how much space to give C:
Type how many GB you want to move and choose C: as the destination. For Windows 11 it’s good to have at least 30–40 GB free on C:.
Enter 60 GB, choose C: and click OK
Space to allocate:
Allocate the space to:
Apply the changes
So far it’s only a preview: nothing has been changed yet. Click Apply in the top left and then Proceed.
Click Apply, then Proceed
Restart in a special mode
Because C: contains Windows, the program finishes the operation during a restart. The PC works on its own for a few minutes: don’t turn it off.
Wait for Windows to restart normally
Other useful operations
- Split a new drive: right-click the unallocated space → Create Partition.
- Merge C: and D:: right-click C: → Merge Partitions. The files from D: end up in a folder on C:.
- Move to an SSD: use Migrate OS to SSD to move just Windows to the new drive.
Frequently asked questions
Could I lose my data?
The operations are designed not to delete anything, but a power cut while they’re running can cause problems. That’s why we recommend a backup before you start, especially on laptops with a low battery.
Can I do this with BitLocker turned on?
It’s best to suspend BitLocker before changing partitions (Control Panel → BitLocker Drive Encryption → Suspend protection) and turn it back on at the end.
What’s the difference between AOMEI and EaseUS?
They handle the same main tasks. AOMEI has the handy “Allocate Free Space” feature, EaseUS a very simple interface with drag-to-resize. Both are lifetime licences for 2 PCs.
Read also
All articles
Edit a PDF Without Adobe: PDFelement, PDFChef or Nitro?
How to edit, sign and convert PDFs without an Adobe subscription: PDFelement, PDFChef and Nitro PDF Pro compared, plus a step-by-step guide.
Video Editing: Filmora vs Movavi Video Suite – Which One to Choose?
Filmora or Movavi Video Suite? Two easy video editors with a lifetime licence compared, free alternatives, and which to pick for social, family or tutorials.
Slow PC: What Really Helps (and What Doesn’t) to Speed It Up
Slow PC? Free checks, what Driver Booster, Avast Cleanup and AVG TuneUp really do, what to avoid and when you need an SSD. With a step-by-step guide.
