Hi,
The final compatabile Essential Studio release with the VS2003 .NET 1.1 is version 5.1.0.51.
You can download the same from the below link.
http://files.syncfusion.com/installs/v5.1.0.51/syncfusionessentialstudiosetup.exePlease try this and let us know if this helps.
Regards,
Nanda
Syncfusion