did you do it properly ??

Code:
SQL*Plus: Release 9.2.0.3.0 - Production on Sat May 10 12:43:29 2003

Copyright (c) 1982, 2002, Oracle Corporation.  All rights reserved.

Enter user-name: sys as sysdba
Enter password:

Connected to:
Oracle9i Enterprise Edition Release 9.2.0.3.0 - Production
With the Partitioning, Oracle Label Security, OLAP and Oracle Data Mining options
JServer Release 9.2.0.3.0 - Production

[email protected]D> shutdown immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
[email protected]D> startup mount
ORACLE instance started.

Total System Global Area  101784796 bytes
Fixed Size                   453852 bytes
Variable Size              75497472 bytes
Database Buffers           25165824 bytes
Redo Buffers                 667648 bytes
Database mounted.
[email protected]D> select name from v$datafile
  2  ;

NAME
----------------------------------------------------------------------------------------------------
E:\ORACLE\ORADATA\ACME\SYSTEM01.DBF
E:\ORACLE\ORADATA\ACME\UNDOTBS01.DBF
E:\ORACLE\ORADATA\ACME\EXAMPLE01.DBF
E:\ORACLE\ORADATA\ACME\INDX01.DBF
E:\ORACLE\ORADATA\ACME\TOOLS01.DBF
E:\ORACLE\ORADATA\ACME\USERS01.DBF
E:\TEST01.DBF
E:\ORACLE\ORADATA\ACME\MNT_S.DBF

8 rows selected.

[email protected]D> alter database rename file 'E:\ORACLE\ORADATA\ACME\SYSTEM01.DBF' to 'E:\ORACLE\ORADATA\SYSTEM01.DBF';

Database altered.

[email protected]D> alter database open;

Database altered.

[email protected]D>
[email protected]D> shutdown immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
[email protected]D> startup mount
ORACLE instance started.

Total System Global Area  101784796 bytes
Fixed Size                   453852 bytes
Variable Size              75497472 bytes
Database Buffers           25165824 bytes
Redo Buffers                 667648 bytes
Database mounted.
[email protected]D> alter database rename file'E:\ORACLE\ORADATA\SYSTEM01.DBF'  to 'E:\ORACLE\ORADATA\ACME\SYSTEM01.DBF';

Database altered.

[email protected]D> alter database open;

Database altered.

[email protected]D>