Generate Solution Manager Key :-
1)Create a system by right clicking on System entry and select Create new system.
2)Enter the System Name i.e., SID (3 chars)
3)Product = SAP ECC (select from the list)
4)Product Version= ECC 5.0 (select from the list)
5)Save the entries.
6)Select Menu Item "System--->Other Configuration" and enter the SID which you have created earlier.
7)Enter the Server Name(hostname)
8)Finally click on Generate "Installation/Upgrade Key Button "
The system generates a Key ,copy that Key and paste it in the SAPINST screen when it prompts for Sol man Key.