CCleaner keeps crashing on Windows 10/11 [Startup, Safe Mode]

by Radu Tyrsina
Radu Tyrsina
Radu Tyrsina
CEO & Founder
Radu Tyrsina has been a Windows fan ever since he got his first PC, a Pentium III (a monster at that time). For most of the kids of... read more
Affiliate Disclosure
  • CCleaner is a very useful tool that scans and deletes unnecessary files to free up space on your computer.
  • Several factors can cause this tool to crash, including a corrupt download or improper installation of the software.
  • For more guides and fixes, head to our Tech Troubleshooting section.
  • If you're looking for more digital tools, you will find lots of awesome articles in our Software Hub.
How to fix CCleaner if it keeps crashing on Windows 10

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If you have been a Windows user for a long time now, then CCleaner is no stranger to you. For starters, CCleaner works to scan and delete unnecessary files to free up space in your computer storage.

These temporary files emerge from programs, report logs, and Internet Explorer files as you open them.

However, the disk cleanup software is unable to remove cache files from other browsers, including Chrome and Firefox.

The tool also clears your browsing history and your most recently opened files. This is especially helpful for users who want to maintain a certain level of privacy.

As a third-party software, CCleaner also helps to resolve computer issues arising from old or corrupted files.

While the software is designed to help fix computer problems, it can sometimes run into an error itself. Users are reporting a crash problem in CCleaner while the tool is running.

Several factors can cause CCleaner to crash (C000021A error), including a corrupt download or improper installation of the software.

The problem also arises after you have modified or updated CCleaner, which can corrupt the Windows registry if the change is incomplete.

Malware infection is another major contributor to CCleaner crash as it corrupts Windows system files or CCleaner files.

However, even non-malware programs can cause CCleaner to crash as well, when files related to the disk cleanup tool are inadvertently deleted upon running those programs. Below is a list of solutions to help you fix CCleaner crashes.

How can I fix CCleaner in Windows 10?

1. Scan your computer for malware

The C000021A error sometimes arises due to the presence of malware on your computer. Malicious software could corrupt and remove runtime-related files.

Many anti-malware programs could help resolve this issue.

A compatible antimalware in Windows 10 should be good for protection, but also for not interfering with other system settings or programs.

After cleaning your computer and solving the problem with CCleaner, you will still have a solution that will also protect you from multi-layered ransomware, online phishing, and fraudulent attempts. 

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Open the tool of your choice, run a system scan, and wait for the process to complete. Of course, you will need to allow it to delete any found threats and to repair and optimize the system.

2. Update device drivers to fix the C000021A error

There’s a good chance that outdated PC device drivers are causing the C000021A error. This is not entirely a cause for so much worry, however. Driver updates are always available to download from software manufacturers.

The challenge, though, is the arduous task of finding the exact driver for C000021A-related device. Worse, installing the wrong driver update can even lead to further issues.

You can also deal with this problem a lot easier by using specialized software to update drivers automatically. There are a few such third-party software but we recommend DriverFix.

Here’s what you need to do:

  1. Download DriverFix
  2. Start the program and wait for it to scan your PC
  3. Select the drivers from the list and wait for their installation
  4. Restart your PC

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3. Perform a manual repair of Windows registry

  1. Backup the registry files related to C000021A error.
  2. Type command in Windows search.
  3. Hold CTRL-Shift on the keyboard before hitting Enter. Select Yes once a permission dialog box appears.
  4. Type regedit  and press Enter.
  5. Then choose CCleaner in the Registry Editor to backup the program before clicking Export in the File menu.
  6. Select a folder in the Save In list where you want to save the CCleaner backup key.
  7. Click Selected branch in the Export Range box before hitting Save. The backup is now saved as a .reg file.

Note: The manual process of editing the Windows registry, is recommended only for advanced computer users. Even the slightest mistake in the use of Registry Editor can cause irreversible problems to your operating system.

4. Remove temporary files and folders

  1. Type command in Windows search.
  2. Hold CTRL-Shift before hitting Enter and a permission dialog box will crop up. Select Yes.
  3. Type cleanmgr and press Enter.
  4. The Windows Disk Cleanup tool will now calculate how much space you can free up and allow you to choose which category you want to clean out.

5. Perform a Windows System Restore

  1. Type restore in Windows search and click on Create a restore point from the results.
  2. Click on System Restore, then on the Next button.
  3. Select a restore point from the list.

Note: If you didn’t create any restore points before, you won’t be able to perform a System Restore.

6. Download and install Windows updates

Microsoft constantly rolls out updates to improve Windows. But most users frequently ignore these updates, inadvertently or otherwise.

These updates, in fact, usually help to fix C000021A errors with the newest Service Pack and the latest patches. To see the latest Windows updates, simply open the Windows Update dialog box and click Install Updates.

7. Use an alternative cleaning software

If all else fails, we recommend you uninstall CCleaner and try an alternative disk cleanup software.

If you merely want to erase all the files before installing a new operating system or doing another regular action, a quick or full format of the disk or partition would suffice.

The tool searches your hard drive for files you no longer require, such as temporary files, cached webpages, and rejected items that wind up in your system’s Recycle Bin.

Disk Clean-up should be performed at least once a month as a preventative maintenance operation. Disk Clean-up may erase temporary internet data, downloaded application files, and offline webpages.

You may also use disk clean-up to clear the recycle bin, erase temporary files, and delete thumbnails.

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