In Oracle9i,startup command will searches for the following files in this order:
1) Search for the spfile$ORACLE_SID.ora file in the default location,
2) If it does not exist, it looks for the spfile.ora; and
3) If this file is not found either, then it searches for the pfile by name init$ORACLE_SID.ora.
If you have no spfile,it will certainly use pfile to start the database.