QuickBooks may stop working due to internal corruption, Windows issues, or antivirus conflicts. To resolve, start by rebooting the system and opening QuickBooks in selective startup mode. Running the QuickBooks Install Diagnostic Tool can repair damaged program files. Additionally, verifying company data with QuickBooks Verify and Rebuild features prevents recurring crashes. Always keep QuickBooks and Windows updated, and ensure proper file permissions for shared folders. Proactive system maintenance and regular backups protect your financial data and help prevent future “stopped working” errors.