Hi,
i noticed this strange thing in registry.
HKEY_LOCAL_MACHINE-->SOFTWARE-->ORACLE folder has a key(entry) ORACLE_HOME as "C:\ORAWIN95".
HKEY_LOCAL_MACHINE-->SOFTWARE-->ORACLE-->ALL_HOMES\ID0 folder has a key PATH as "D:\ORACLE\ORA90"
HKEY_LOCAL_MACHINE-->SOFTWARE-->ORACLE-->HOME0 folder has a key
NLS_LANG as AMERICAN_AMERICA.WE8MSWIN1252.
HKEY_LOCAL_MACHINE-->SOFTWARE-->ORACLE-->HOME0 folder has a key ORACLE_HOME as "D:\ORACLE\ORA90".

i hope this information helps. Thanks for all ur replies.

Also I went to registry HKEY_LOCAL_MACHINE-->SOFTWARE-->ORACLE . In this ORACLE folder i found NLS_LANG entry which had a value of "NA" and changed it to value which someone told me should be this i.e AMERICAN_AMERICA.WE8ISO8859P1 . I tried to logon thru sqlplus with scott/tiger and I got this message box " ORA 205 CANNOT MOUNT DATABASE" with title of message window as Oracle 8 startup. Also sql plus had this message
ERROR:
ORA-01034: ORACLE not available
ORA-09243: smsget: error attaching to SGA
OSD-04101: invalid SGA: SGA not initialized.

Then i went to HKEY_LOCAL_MACHINE-->SOFTWARE-->ORACLE--> ALL_HOMES-->ID0. In ID0 folder too i changed the NLS_LANG to the same value but still got the same message pasted above. I also tried the command prompt method
c:\> set NLS_LANG=AMERICAN_AMERICA.WE8ISO8859P1
c:\> set oracle_sid=......
c:\> sqlplus /nolog
SQL> connect / as sysdba
I get thru first few steps but when i got the SQL PROMPT and tried to login as sysdba but got the same message i.e
ERROR:
ORA-01034: ORACLE not available
ORA-09243: smsget: error attaching to SGA
OSD-04101: invalid SGA: SGA not initialized.

I dont know what to do now.

Someone xyz said "Try either matching the NLS_LANG parmeter or remove it. If there is no NLS_LANG parameter in the environment, the application will use what the database server passes back to it."

I deleted the NLS_LANG parameter from HKEY_LOCAL_MACHINE-->SOFTWARE-->ORACLE folder but i got same message which i got by changing the NLS_LANG.

Any suggestions are welcome.P.S why iam not getting email notification when someone is replying to my post. I had checked the box for automatic notification. Sorry for posting this issue but I had to literally check myself if someone replied or not.