Hi Andreas,
Thanks for using Syncfusion products.
Could you please follow the steps mentioned below to manually remove the setup from the machine.
1. Please download and install the Windows Installer cleanup utility from the following download link:
https://s3.amazonaws.com/files2.syncfusion.com/Installs/Cleanup/msicuu2.exe
2. Remove all the Syncfusion product related installers using Windows Installer Clean up utility.
3. Then, manually delete the Syncfusion installed files(entire 10.3.0.43 folder) from the following location (if exists).
Source (Windows XP, Windows Vista, Windows 7): C:\Program Files\Syncfusion\Essential Studio\
Samples (Windows XP): C:\Syncfusion\
Samples (Windows Vista, Windows 7): C:\Users\{user name}\AppData\Local\Syncfusion\EssentialStudio\
4. Then, again install the Syncfusion Essential Studio setup (v10.3.0.43) with corresponding unlock key.
Please let us know, if you have any queries.
Regards,
Sivaguru S