Originally posted by amitstora
I had tried both ways i.e.,by setting new key in the registry in HKEY_LOCAL_MACHINE/SOFTWARE/ORACLE/ORACLE_HOME
and also by setting in the new string as:

variable name:NLS_DATE_FORMAT
VALUED-MON-YYYY
I'm not sure I understand exactly what you have done, but I suspect you have set the NLS_DATE_FORMAT variable in the registry keyHKEY_LOCAL_MACHINE/SOFTWARE/ORACLE/ORACLE_HOMES, which is not correct place for this setting. Set it in the following key:
HKEY_LOCAL_MACHINE/SOFTWARE/ORACLE/HOME0. If you have more than one oracle_home then it might also be HOME1 or HOME2 or HOMEn instead of HOME0 - determine which home is the right one for the tool/aplication you are using and set NLS_DATE_FORMAT there.