Product authorization and licensing for Desktop, Enterprise, Engine and ArcGIS extensions are available through My Esri.

ArcSDE 10 & ArcIMS 10 Authorizations - Generate an Esri authorization file for ArcSDE 10 or ArcIMS 10 for UNIX or Linux.

8.x & 9.x Single Use Product Registration - for Single Use software (ArcView, ArcEditor and extensions), Server software (ArcSDE, ArcIMS, ArcGIS Server and extensions), Developer software (ArcGIS Engine) and other software installed on only one machine

8.x & 9.x License File Request  - if you are an existing Concurrent Use ArcGIS customer who has made changes to your license server or license allocation for ArcInfo, ArcEditor, ArcView and their extensions