Go to your computer's Control Panel > Add or Remove Programs (or Programs and Features ) and uninstall Adobe Audition 1.5.
To change the user interface language, you must select the desired language during the initial installation setup: Backup Your Data how to change language in adobe audition 1.5
No. Adobe Audition 1.5 predates the Creative Cloud system. While newer versions (like Audition CC) allow language changes via the Creative Cloud Desktop app, version 1.5 requires a manual reinstall. Go to your computer's Control Panel > Add
Follow the rest of the installation prompts (installation path, registration, etc.). Once finished, launch Adobe Audition 1.5. Troubleshooting: What if I Don't Have the Installer? etc.). Once finished