It would help if you let us know which version of Oracle RDBMS you are using. On NT, the autostarting mechanism is very different on various sub-versions of Oracle7.*, it is again different on Oracle8.0 and again totaly different on 8.1.
One of frequent reasons that autostart doesn't work is when the password for INTERNAL is changed in the database, but is not changed in batch file that is fired during the autostart. In 7.3 and 8.0 you'll find a file STRT.CMD in your %ORACLE_HOME%\DATABASE. There you'll find the switch "-usrpwd " followed by the internal password (default is ORACLE). If it does not match the internal password of your instance, you can change this password in your bartch file or you could reset the instance password to the value written in your bach file using ORAPWDxx.EXE. Or even better, you could reset and synchronise the internal password in your batch file and your database instance by using ORADIMxx.EXE.
HTH,
