Originally posted by Gus

My Initialisation parameter file (G:\ORACLE\ORA81\DATABASE\INITmydb.ORA) contains the following...
db_name = mydb
service_names = myse
instance_name = myin
Is this the entire init.ora? Are you following OFA? Otherwise you have to specify some more parameters.

The only way I can get the database to open is to explicitly issue ....
STARTUP PFILE=G:\ORACLE\ORA81\DATABASE\INITmydb.ORA
This is normal behaviour. I do this all the time.

Additionally I have recreated the service using ORADIM
ORADIM -new -sid myin -intpwd oracle -startmode a -pfile G:\ORACLE\ORA81\DATABASE\INITmydb.ORA

....but I still get ...
LRM-00109 could not open parameter file 'G:\ORACLE\ORA81\DATABASE\INITmyin.ORA'
Why are you re-installing the service, while you can open the database via "STARTUP PFILE=G:\ORACLE\ORA81\DATABASE\INITmydb.ORA"?

Are you sure that Oracle can find the init.ora on that path? Is the ASCII-file in use maybe? Or corrupt? If Oracle says it can't open the file, it really can't open it. So check the path and check to see if the file is still plain ASCII (don't open it in some editor and save it as MS Word or something like that).

HTH,
Erik