Daemon Tools Lite is inherently free for personal, non-commercial use. You do not need a paid serial number or a third-party .txt file to use its core features. During installation from the official developer website, simply select the Free License (with ads) option.

Bypassing software licensing violates the developer's terms of service. Proper Way to Use DAEMON Tools Lite

: Convert physical optical discs into virtual images for backup and easy access.

What (ISO, VHD, NRG, etc.) you are trying to open? Which operating system version you are currently running?