OPatch failed with error code = 74 (Windows)

Recently I had to patch one 10g on Win x64. As I', pretty new to Windows and Oracle environments, I thought that shutting down all Oracle based services should be enough step for patching but I was wrong.
When I tried to apply patch I got:

C:\oracle\install\p8609347_10204_MSWIN-x86-64\8609347>opatch apply
Invoking OPatch 10.2.0.5.0

Oracle Interim Patch Installer version 10.2.0.5.0
Copyright (c) 2010, Oracle Corporation.  All rights reserved.


Oracle Home       : C:\oracle\product\10.2.0\db_1
Central Inventory : C:\oracle\Inventory
   from           : n/a
OPatch version    : 10.2.0.5.0
OUI version       : 10.2.0.4.0
OUI location      : C:\oracle\product\10.2.0\db_1\oui
Log file location : C:\oracle\product\10.2.0\db_1\cfgtoollogs\opatch\opatch2010-09-13_08-54-22AM.log

Patch history file: C:\oracle\product\10.2.0\db_1\cfgtoollogs\opatch\opatch_history.txt

ApplySession applying interim patch '8609347' to OH 'C:\oracle\product\10.2.0\db_1'
Interim patch 8609347 is a superset of the patch(es) [  8609347 ] in the Oracle Home
OPatch will rollback the subset patches and apply the given patch.

Running prerequisite checks...
Prerequisite check "CheckActiveFilesAndExecutables" failed.
The details are:

Following files are active :
C:\oracle\product\10.2.0\db_1\bin\oraclient10.dll
C:\oracle\product\10.2.0\db_1\bin\orapls10.dll
C:\oracle\product\10.2.0\db_1\bin\oracommon10.dll
C:\oracle\product\10.2.0\db_1\bin\orageneric10.dll
C:\oracle\product\10.2.0\db_1\rdbms\admin\oraclient10.sym
C:\oracle\product\10.2.0\db_1\rdbms\admin\orapls10.sym
C:\oracle\product\10.2.0\db_1\rdbms\admin\oracommon10.sym
C:\oracle\product\10.2.0\db_1\rdbms\admin\orageneric10.sym
C:\oracle\product\10.2.0\db_1\bin\oraimr10.dll
C:\oracle\product\10.2.0\db_1\bin\oraplp10.dll
C:\oracle\product\10.2.0\db_1\rdbms\admin\oraplp10.sym
C:\oracle\product\10.2.0\db_1\bin\oracle.exe
C:\oracle\product\10.2.0\db_1\rdbms\admin\oracle.sym
C:\oracle\product\10.2.0\db_1\bin\orajox10.dll
C:\oracle\product\10.2.0\db_1\bin\oranls10.dll
C:\oracle\product\10.2.0\db_1\rdbms\admin\oranls10.sym
C:\oracle\product\10.2.0\db_1\bin\orasnls10.dll
C:\oracle\product\10.2.0\db_1\rdbms\admin\orasnls10.sym
C:\oracle\product\10.2.0\db_1\bin\oran10.dll
C:\oracle\product\10.2.0\db_1\bin\oranl10.dll
C:\oracle\product\10.2.0\db_1\bin\orannzsbb10.dll
C:\oracle\product\10.2.0\db_1\bin\oracore10.dll
C:\oracle\product\10.2.0\db_1\rdbms\admin\oracore10.sym
C:\oracle\product\10.2.0\db_1\bin\orahasgen10.dll
C:\oracle\product\10.2.0\db_1\bin\orahasgen10.dll
C:\oracle\product\10.2.0\db_1\rdbms\admin\orahasgen10.sym
C:\oracle\product\10.2.0\db_1\bin\oraocr10.dll
C:\oracle\product\10.2.0\db_1\rdbms\admin\oraocr10.sym
C:\oracle\product\10.2.0\db_1\bin\oraocrb10.dll
C:\oracle\product\10.2.0\db_1\rdbms\admin\oraocrb10.sym
C:\oracle\product\10.2.0\db_1\bin\oraldapclnt10.dll
C:\oracle\product\10.2.0\db_1\bin\oraxml10.dll
ApplySession failed during prerequisite checks: Prerequisite check "CheckActiveFilesAndExecutables" failed.
System intact, OPatch will not attempt to restore the system
--------------------------------------------------------------------------------
The following warnings have occurred during OPatch execution:
--------------------------------------------------------------------------------

OPatch failed with error code = 74

C:\oracle\install\p8609347_10204_MSWIN-x86-64\8609347>

The solution

Killing Windows processes that holds some DLLs are not so easy when you have to kill something else then Explorer or there were several blocked DLLS (at it was in mine case).

So I found out nice freeware utility Unlocker which is made for 32 as well as 64 bit Windows versions. It's advantage over Who's Locking?, which I was using until now, is that Unlocker can release all locks on whole directory in one step.

Cheers!