Hello Kanne,
To configure SNC with SSO for SAPGUI based on your AD Domain, you can use SAP Single Sign-On product (which also provides a lot of other SSO functionalities). For more information regarding this product, please refer to its site:
SAP Single Sign-On 2.0 – SAP Help Portal Page
Product Implementation Guide:
http://help.sap.com/download/sapsso/secure_login_impl_guide_en.pdf
Best Regards,
Guilherme de Oliveira
SAP Active Global Support