I tried your solution . It is not working for me ..I simulated the problem on my test box . I renamed the system1.dbf to temp.dbf and tried to startup with _allow_resetlogs_corruption=true entry in init.ora ..

ORA-01157: cannot identify/lock data file 1 - see DBWR trace file
ORA-01110: data file 1: 'D:\KELLER\KELLER\SYSTEM01.DBF'