control file and redo log

[RJP]

here is the real example:

>startup mount; (can not open becasue control file restored from backup)
> select group#, status from v$log;

GROUP# STATUS
---------- ----------------
1 INACTIVE
2 CURRENT
3 INACTIVE
>alter system drop logfile group 1;
>alter system add logfile group 1 '/ora.......
>alter system drop logfile group 3;
>alter system add logfile group 3 '/ora.......
> select group#, status from v$log;

GROUP# STATUS
---------- ----------------
1 UNUSED
2 CURRENT
3 UNUSED
now how I drop group2?
without system open I can not do:
alter system switch logfile;

I dooooommmmed? any solution?