While migrating to NDS V 2.7.5 follow the undermentioned steps
1) Uninstall the Member Server(Refer document Procedure for uninstalling the Member Server .doc)
2) Install Member Server(Refer document Upgradation Mannual For NDS V.2.7.5.doc)
once member server is successful 
3) Uninstall the Member (Refer document Procedure for uninstalling the Member Client .doc)
4) Install the member clients(Refer document Upgradation Mannual For NDS V.2.7.5.doc)

Incase while installing member clients, the Clients throw the error "Active X component cannot creat object" perform the steps given in the document ActiveXError.doc.

In case of fresh installation on a new server/client refer documents Fresh Server Installation of NDS V.2.7.5.doc and Fresh Client Installation of NDS Ver 2.7.5.doc