C drive turning red is a common headache for Windows users—system update cache, temp files, desktop files, WeChat chat records… Before you know it, your C drive is packed. Replacing the hard drive is expensive, and cleaning only treats the symptoms. The most thorough solution is: borrow space from other drives for your C drive.

📦 Preparation

⚡ In a nutshell: Put Windows into a “hibernation box” so the C drive isn’t occupied.

① Download WePE Toolbox

WePE Toolbox — a lightweight PE (Preinstallation Environment) tool, clean and ad-free.

② Install to System

Open the downloaded program and click 「Install into System Now」. It will automatically write the boot entry.

③ Reboot into Boot Menu

After installation, restart your computer. You’ll see the system boot selection screen.

⏱ Note: The countdown is only a few seconds. If it times out, it will boot into the current system. Watch closely and select quickly!

④ Enter PE Environment

Use arrow keys to select WePE Toolbox and press Enter.

💡 Why enter PE?

In the PE environment, your Windows system is completely “hibernated”—the C drive is not occupied by any process. This allows safe partition resizing. Think of it like surgery: the patient must be anesthetized before the operation. Other partition tools work on the same principle.

🛠️ Resize

Once in PE, the tool menu will pop up automatically. Click 「Partition Assistant」.

Step 1 · Check Disk Layout

Partition Assistant will show you the layout of all disk partitions. Identify which drive has free space to “donate” to the C drive.

Step 2 · Choose the Drive to Shrink

Here we use Software (D drive) as an example. We’ll “cut” some space from D drive to give to C drive.

💡 Which drive to choose?

• ✅ Prefer drives with plenty of free space that you don’t use often
• ❌ Avoid touching system recovery partitions or EFI partitions

Step 3 · Adjust Partition

Right-click D drive → 「Adjust Partition」.

Step 4 · Shrink the Drive

In the popup window, drag the slider or enter a value to decide how much space to take from D drive.

✅ Example: If you want to add 50GB to C drive, shrink D drive by 50GB here.

⚠️ Note: The shrink value must not exceed the used space on D drive, or it will error.

Click 「OK」 when done.

Step 5 · Merge into C Drive

You’ll now see a block of 「Unallocated Space」 next to D drive.

Step 6 · Submit Task

Click 「Submit」 in the top-left corner.

⚠️ Critical Reminder

All the adjustments so far are just “plans” — they haven’t taken effect yet.

Only after clicking 「Submit」 will the system actually execute the partition operations. Double-check before submitting!

Step 7 · Wait for Execution

Partition Assistant will begin executing the adjustments. This may take several minutes to over ten minutes, depending on your disk size and speed.

Step 8 · Done 🎉

When you see the success message, the expansion is complete!

🚀 Reboot & Cleanup

🧹 Final step: If you don’t want to see the boot selection screen every time, open WePE Toolbox → click 「Uninstall」 to restore the original state.

📌 Tips

✨ That's the complete guide to expanding your C drive. May your computer never see red again!