SQL 2005 Install Fails Immediately

I've had my problems with installing DPM before, but this was a new one!  DPM setup started ok, but as soon as it got to the SQL install portion, the installer failed, with this error message:

Microsoft SQL Server 2005 Setup
SQL Server Setup unexpectedly failed. For more information, review the Setup summary log file in %ProgramFiles%\Microsoft SQL Server\90\Setup Bootstrap\LOG\Summary.txt.

The setup log wasn't much help either:

Microsoft SQL Server 2005 9.00.1399.06
==============================
OS Version      : Microsoft Windows Server 2003 family, Enterprise Edition Service Pack 2 (Build 3790)
Time            : Wed Oct 22 15:29:15 2008

Yeah, lots of help there... thanks...

Well, there is a folder ( %ProgramFiles%\Microsoft SQL Server\90\Setup Bootstrap\LOG\Files ) that had a couple of log files too, and it led me towards actual errors:

Microsoft SQL Server 2005 Setup beginning at Mon Oct 20 17:07:59 2008
Process ID      : 3364
D:\Sources\DPM2007\64bit\DPM2007_64bit\SQLSVR2005\Servers\setup.exe Version: 2005.90.1399.0
Running: LoadResourcesAction at: 2008/9/20 17:7:59
Complete: LoadResourcesAction at: 2008/9/20 17:7:59, returned true
Running: ParseBootstrapOptionsAction at: 2008/9/20 17:7:59
Loaded DLL:D:\Sources\DPM2007\64bit\DPM2007_64bit\SQLSVR2005\Servers\xmlrw.dll Version:2.0.3604.0
Complete: ParseBootstrapOptionsAction at: 2008/9/20 17:7:59, returned false
Error: Action "ParseBootstrapOptionsAction" failed during execution.  Error information reported during run:
Could not parse command line due to datastore exception.
  Source File Name: utillib\persisthelpers.cpp
Compiler Timestamp: Fri Jul 29 01:13:55 2005
     Function Name: writeEncryptedString
Source Line Number: 124
----------------------------------------------------------
writeEncryptedString() failed
      Source File Name: utillib\persisthelpers.cpp
    Compiler Timestamp: Fri Jul 29 01:13:55 2005
         Function Name: writeEncryptedString
    Source Line Number: 123
    ----------------------------------------------------------
            Error Code: 0x80070002 (2)
Windows Error Text: The system cannot find the file specified.

  Source File Name: cryptohelper\cryptsameusersamemachine.cpp
Compiler Timestamp: Mon Jun 13 14:30:00 2005
     Function Name: sqls::CryptSameUserSameMachine::ProtectData
Source Line Number: 50

2
Could not skip Component update due to datastore exception.
  Source File Name: datastore\cachedpropertycollection.cpp
Compiler Timestamp: Fri Jul 29 01:13:49 2005
     Function Name: CachedPropertyCollection::findProperty
Source Line Number: 130
----------------------------------------------------------
Failed to find property "InstallMediaPath" {"SetupBootstrapOptionsScope", "", "3364"} in cache
      Source File Name: datastore\propertycollection.cpp
    Compiler Timestamp: Fri Jul 29 01:13:50 2005
         Function Name: SetupBootstrapOptionsScope.InstallMediaPath
    Source Line Number: 44
    ----------------------------------------------------------
    No collector registered for scope: "SetupBootstrapOptionsScope"
Running: ValidateWinNTAction at: 2008/9/20 17:7:59
Complete: ValidateWinNTAction at: 2008/9/20 17:7:59, returned true
Running: ValidateMinOSAction at: 2008/9/20 17:7:59
Complete: ValidateMinOSAction at: 2008/9/20 17:7:59, returned true
Running: PerformSCCAction at: 2008/9/20 17:7:59
Complete: PerformSCCAction at: 2008/9/20 17:7:59, returned true
Running: ActivateLoggingAction at: 2008/9/20 17:7:59
Error: Action "ActivateLoggingAction" threw an exception during execution.  Error information reported during run:
Datastore exception while trying to write logging properties.
  Source File Name: datastore\cachedpropertycollection.cpp
Compiler Timestamp: Fri Jul 29 01:13:49 2005
     Function Name: CachedPropertyCollection::findProperty
Source Line Number: 130
----------------------------------------------------------
Failed to find property "primaryLogFiles" {"SetupStateScope", "", ""} in cache
      Source File Name: datastore\propertycollection.cpp
    Compiler Timestamp: Fri Jul 29 01:13:50 2005
         Function Name: SetupStateScope.primaryLogFiles
    Source Line Number: 44
    ----------------------------------------------------------
    No collector registered for scope: "SetupStateScope"
0000000000F4AF90Unable to proceed with setup, there was a command line parsing error. : 2
        Error Code: 0x80070002 (2)
Windows Error Text: The system cannot find the file specified.

  Source File Name: datastore\propertycollection.cpp
Compiler Timestamp: Fri Jul 29 01:13:50 2005
     Function Name: SetupBootstrapOptionsScope.InstallMediaPath
Source Line Number: 44

Class not registered.
Failed to create CAB file due to datastore exception
  Source File Name: datastore\cachedpropertycollection.cpp
Compiler Timestamp: Fri Jul 29 01:13:49 2005
     Function Name: CachedPropertyCollection::findProperty
Source Line Number: 130
----------------------------------------------------------
Failed to find property "HostSetup" {"SetupBootstrapOptionsScope", "", "3364"} in cache
      Source File Name: datastore\propertycollection.cpp
    Compiler Timestamp: Fri Jul 29 01:13:50 2005
         Function Name: SetupBootstrapOptionsScope.HostSetup
    Source Line Number: 44
    ----------------------------------------------------------
    No collector registered for scope: "SetupBootstrapOptionsScope"
Message pump returning: 2

Looked like a dump to me.  Well, long story short, and a couple of days of frustration, I found out that the OS was a custom install by the server team, and it was a custom install.  Needless to say, I was just missing one registry key.

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\User
Shell Folders\AppData

It seems the key had been messed up in the build of the OS. The key should be a REG_EXPAND_SZ and set to:

%USERPROFILE%\Application Data

Hope this helps somebody!