Cenvat Credit

you can take benefit of service tax under excise

central excise duty paid means, capital goods 

if the duty paid goods qualify as capital goods and are needed for providing taxable services, then you can take input credit as per CCR2004 ( 50% in 1st year and balance in subsequent year), 

No doubt you can avail Cenvat Credit for Excise Duty and use it for payment of Service Tax provided other conditions of Relevant rules are fulfilled. No need to register under Excise Act.