We explain how you can clean your Windows operating system using CCleaner's Custom Clean. If you want to find out more about your operating system's specific cleaning rules in CCleaner, skip to Files and data in your Windows operating system (advanced) below.  

What is Custom Clean?

Custom Clean is a function within CCleaner that allows you to customize how the app cleans different parts of your PC, such as your operating system and applications (like web browsers).

What are 'cleaning rules'? 

These are the specific files and data that you allow CCleaner to delete from your system. You can see some in the screenshot below as checkboxes you can select beneath the Windows tab, including the highlighted Advanced section.

We recommend only using these options for troubleshooting:

None of these Cleaning rules are enabled by default, and we recommend only enabling them for specific troubleshooting purposes. They may cause problems otherwise.

Files and data in your Windows operating system (advanced):

• Windows Event Logs - This will clear the entries in your Windows Event Viewer, which can often be used to diagnose problems occurring with your computer but can typically be deleted if the computer is working properly.
• Old Prefetch Data - To run quickly, Windows uses prefetch files to store information about programs that you frequently use. The cleaner can delete the prefetch data, clearing up space if there are many cached programs that no longer exist or haven't been used for a long time.
• Menu Order Cache - When you drag and drop items on the Start menu into different locations, Windows stores this information in the Menu Order Cache.
• Tray Notifications Cache - This cache stores information about any items that have ever appeared in your System Tray and whether or not you have set them to Hide, Hide When Inactive, or Always Show.
• Window Size/Location Cache - When you open and close Windows Explorer, Windows records folder settings for window position, sort order, columns, folder type, toolbar toggles, and search result views.
• Environment Path - This Cleaning Rule will clear the “PATH” User Variable in your system environment variables back to its default. Find out more. 
• User Assist History - User Assist History is a built-in monitoring feature of Windows that records when you access programs, shortcuts, Control Panel applets, and possibly even web sites.
• IIS Log Files - Microsoft's IIS server keeps logs of its activities on your system. Find out more. 
• Custom Files and Folders - This setting relates to CCleaner rather than any part of Windows. If you select Custom Files and Folders, CCleaner will use the information in the Options > Include list to add folders and Registry keys while cleaning.
• Wipe Free Space - When you delete files from your hard drive, Windows only deletes the reference to the files - but not the files themselves. Over time, the contents of the files get overwritten as Windows writes new files. It's possible to recover some or all parts of the deleted files. 
  • You can prevent this by using the Wipe Free Space option. Find out more. 
  • Note: This will perform a one-pass Wipe Free Space operation; to utilize a higher number of passes, please use the Drive Wiper tool.
• Old Windows installation - When installing a new version of Windows or a major system update (such as a Service Pack) on your computer, there is often the option to save a backup of the old operating system to be reverted to in case of problems. Performing a cleaning with this option enabled will remove this backup, saving a considerable amount of disk space but preventing you from reverting to that old version.