How to fix error driver-irql-not-less-or-equal in CCleaner

Solution Steps

1. 1 Restart CCleaner completely. Close it, open Task Manager (Ctrl+Shift+Esc), find any remaining CCleaner processes, right-click → End Task. Background processes from previous sessions are the most common cause of startup crashes.
2. 2 Update CCleaner to the latest version. Open the app, go to Help → Check for Updates (or download the latest installer from the official website). Updates fix known bugs and compatibility issues.
3. 3 Reset CCleaner settings. Navigate to %APPDATA%\CCleaner and rename the settings folder to add '.old'. This forces CCleaner to create fresh settings — corrupted config files cause crashes.
4. 4 Run CCleaner as Administrator. Right-click the shortcut → Properties → Compatibility → check 'Run as Administrator'. Some features of CCleaner require elevated permissions.
5. 5 Check if CCleaner conflicts with your antivirus. Temporarily disable real-time protection and test. Add CCleaner installation folder to antivirus exclusions.
6. 6 Clear CCleaner cache. Navigate to %LOCALAPPDATA%\CCleaner\Cache and delete all files. Corrupted cache data causes rendering and processing errors.
7. 7 Repair CCleaner installation. Windows Settings → Apps → CCleaner → Modify → Repair. This replaces damaged program files while preserving your data.
8. 8 If CCleaner still won't work: uninstall from Settings → Apps, restart, reinstall from official website. A clean install is the nuclear option but fixes almost everything.