If you are able to login as DDIC or other Admin User Name , login and change the password of sap* . If you dont know any other admin passwords, the way left is delete the row of sap* from the Table usr02 .
Query is :
delete from usr02 where BNAME='sap*' AND MANDT='000';
In MS SQL, using Enterprise manager , delete the Entire row of BNAME=sap* and MANDIT=000 .
Note that the Profile parameter : login/no_automatic_login_sapstart should be set as 0 .
Otherwise go to rz10 > Extended maintanance > Select Instance parameter > Set the parameter login/no_automatic_login_sap* =0 , copy and save.
Restart the instance . You ll be able to login as sap* .