To fix the blue screen error when using the Realtek High Definition Audio Driver on Windows 7, you can try the following steps:
1. Update the driver to the latest version available from the Realtek website.
2. Uninstall the current driver and then reinstall it.
3. Run a system scan to check for any malware or viruses that might be causing the issue.
4. Check for any conflicting drivers and disable or update them.
5. If the issue persists, you may need to seek further assistance from Realtek support or a technical expert.