hi all oracle guru's,
i had a database(v9i) on my winxp system. i dropped the database and re created a new db. now everytime at the command prompt i have to type this:

C:> set ORACLE_SID=mydb

and then login to the sqlplus.

Is there any way that i can set this so that i dont have to enter everytime and how do i do that.

any suggestions would be gr8.