Windows crashes can occur for various hardware and software reasons. When a crash occurs, the blue screen of death (BSOD) appears displaying a stop code that can help troubleshoot the issue. Common causes of crashes include viruses, faulty hardware like a failing power supply, overheating issues, driver or software conflicts, and memory/motherboard problems. It is important to keep systems updated, use antivirus software, and ensure proper cooling/ventilation to help prevent crashes.