Windows 7: Running application using App Paths vs Batch File - windows

Question

I have an (PowerBuilder) application (let's call it MyApp.exe) in a folder with a sub-directory that has all the required dlls. I am able to run this application, by adding the application path and associated path variable to Windows App Paths registry key.
[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Windows\CurrentVersion\App Paths\MyApp.EXE]
"Path"="C:\\Prog32\\MyAPP;C:\\Prog32\\MyAPP\\DLL\\;"
#="C:\\Prog32\\MyApp\\MyApp.EXE"
The above runs file. I didn't even have to register DLLs.
If possible, I would like to run it using a batch file though, as users may install multiple versions of the same application in separate folders. When I tried to do the same thing in a batch file, it cannot find the DLLs.
#SETLOCAL
SET CURDIR=%~dp0
CD %CURDIR%
PUSHD %CURDIR%
SET PATH=%CURDIR%;%CURDIR%\dll;%PATH%
start "" %CURDIR%\myApp.exe
POPD
ENDLOCAL
I created this batch in the same directory as the executable, MyApp.exe. I was expecting it would find the DLLs, same way App Paths PATH setting did. The Batch file errors out not being able to find the DLLs. Do we need to register DLLs in this case? Why is it treated differently?
Notes:
If I copied all the required DLLs to the same directory as the executable (without a DLL sub-directory), it runs fine without needing to worry about PATH or registering dlls.
We used to use installShield to install before, but admins have automated scripts to copy files, they shied away from InstallShield programs after the first install. I am trying to refine the process, so what they copy will be simplified.
Thanks in advance for all your valuable comments and suggestions.-Sam

Answer 1

Why is it treated differently?
Because Windows is a mess when searching for libraries. See http://msdn.microsoft.com/en-us/library/windows/desktop/ms682586.aspx#search_order_for_desktop_applications
There are many elements to how the search order is determined, but in general it is like this
Check for the library...
already loaded in memory
on the KnownDLL list
in the application's directory
in the System directory
in the 16-bit System directory
in the Windows directory
in the current working directory
in the directories listed in the PATH environment variable
Overall I would agree with what MSDN states on their DLL Redirection page
It is good practice to install application DLLs in the same directory that contains the application
However, if using sub-folders is how you want to organize your application,
you might take a look into using Application Manifests. Something else to try would be to set the library directory as the working directory
#ECHO off
SETLOCAL
SET "CURDIR=%~dp0"
PUSHD "%CURDIR%\dll"
start "" /D "%CURDIR%\dll" "%CURDIR%\myApp.exe"
POPD
ENDLOCAL