Thans for your input. I tried recreating the controlefiles. Now when I try to open the database I get:
ERROR at line 1:
ORA-01194: file 1 needs more recovery to be consistent
ORA-01110: data file 1: 'E:\ORACLE\ORADATA\TRAIN1\SYSTEM01.DBF'

I don't mind if I can open the database in an inconsistent state.

Any expert opinion welcomed.