Updating reading and updating a single entry in Reg file

This is mostly directed at Prapper since I am modifying his launcher for Glary Utilities.

I am creating a launcher for CUE Splitter which only creates a registry file. I am trying to implement language switching in the launcher, but since the language is stored in the registry file, I'm not really sure how to update it. I have included the code below, but it obviously doesn't work. Any help would be appreciated.

Thanks.

;Copyright 2004-2010 John T. Haller
;Copyright 2008-2010 Devo

;Website: http://PortableApps.com/CUESplitterPortable

;This software is OSI Certified Open Source Software.
;OSI Certified is a certification mark of the Open Source Initiative.

;This program is free software; you can redistribute it and/or
;modify it under the terms of the GNU General Public License
;as published by the Free Software Foundation; either version 2
;of the License, or (at your option) any later version.

;This program is distributed in the hope that it will be useful,
;but WITHOUT ANY WARRANTY; without even the implied warranty of
;MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;GNU General Public License for more details.

;You should have received a copy of the GNU General Public License
;along with this program; if not, write to the Free Software
;Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.

!define PORTABLEAPPNAME "CUE Splitter Portable"
!define APPNAME "CUE Splitter"
!define NAME "CUESplitterPortable"
!define VER "1.6.8.0"
!define WEBSITE "PortableApps.com/CUESplitterPortable"
!define DEFAULTEXE "CUE_Splitter.exe"
!define DEFAULTAPPDIR "CUESplitter"
!define DEFAULTSETTINGSDIR "settings"
!define LAUNCHERLANGUAGE "English"

;=== Program Details
Name "${PORTABLEAPPNAME}"
OutFile "..\..\${NAME}.exe"
Caption "${PORTABLEAPPNAME} | PortableApps.com"
VIProductVersion "${VER}"
VIAddVersionKey ProductName "${PORTABLEAPPNAME}"
VIAddVersionKey Comments "Allows ${APPNAME} to be run from a removable drive.  For additional details, visit ${WEBSITE}"
VIAddVersionKey CompanyName "PortableApps.com"
VIAddVersionKey LegalCopyright "PortableApps.com & Contributors"
VIAddVersionKey FileDescription "${PORTABLEAPPNAME}"
VIAddVersionKey FileVersion "${VER}"
VIAddVersionKey ProductVersion "${VER}"
VIAddVersionKey InternalName "${PORTABLEAPPNAME}"
VIAddVersionKey LegalTrademarks "PortableApps.com is a Trademark of Rare Ideas, LLC."
VIAddVersionKey OriginalFilename "${NAME}.exe"
;VIAddVersionKey PrivateBuild ""
;VIAddVersionKey SpecialBuild ""

;=== Runtime Switches
CRCCheck On
WindowIcon Off
SilentInstall Silent
AutoCloseWindow True
RequestExecutionLevel user
XPStyle On

; Best Compression
SetCompress Auto
SetCompressor /SOLID lzma
SetCompressorDictSize 32
SetDatablockOptimize On

;=== Include
;(Standard NSIS)
!include FileFunc.nsh
!insertmacro GetParameters
!include LogicLib.nsh
!include Registry.nsh

;(Custom)
!include ReadINIStrWithDefault.nsh

;=== Program Icon
Icon "..\..\App\AppInfo\appicon.ico"

;=== Languages
LoadLanguageFile "${NSISDIR}\Contrib\Language files\${LAUNCHERLANGUAGE}.nlf"
!include PortableApps.comLauncherLANG_${LAUNCHERLANGUAGE}.nsh

Var PROGRAMDIRECTORY
Var SETTINGSDIRECTORY
Var ADDITIONALPARAMETERS
Var EXECSTRING
Var PROGRAMEXECUTABLE
Var INIPATH
Var DISABLESPLASHSCREEN
Var SECONDARYLAUNCH
Var LASTPLUGINSDIRECTORY
Var LASTSTARTUP
Var MISSINGFILEORPATH
Var APPLANGUAGE

Section "Main"
	;=== Check if already running
	System::Call 'kernel32::CreateMutexA(i 0, i 0, t "${NAME}") i .r1 ?e'
	Pop $0
	StrCmp $0 0 CheckINI
		StrCpy $SECONDARYLAUNCH "true"

	CheckINI:
		;=== Find the INI file, if there is one
		IfFileExists "$EXEDIR\${NAME}.ini" "" NoINI
			StrCpy $INIPATH "$EXEDIR"

		;=== Read the parameters from the INI file
		${ReadINIStrWithDefault} $0 "$INIPATH\${NAME}.ini" "${NAME}" "${APPNAME}Directory" "App\${DEFAULTAPPDIR}"
		StrCpy $PROGRAMDIRECTORY "$EXEDIR\$0"
		${ReadINIStrWithDefault} $0 "$INIPATH\${NAME}.ini" "${NAME}" "SettingsDirectory" "Data\${DEFAULTSETTINGSDIR}"
		StrCpy $SETTINGSDIRECTORY "$EXEDIR\$0"
		${ReadINIStrWithDefault} $PROGRAMEXECUTABLE "$INIPATH\${NAME}.ini" "${NAME}" "${APPNAME}Executable" "${DEFAULTEXE}"
		${ReadINIStrWithDefault} $ADDITIONALPARAMETERS "$INIPATH\${NAME}.ini" "${NAME}" "AdditionalParameters" ""
		${ReadINIStrWithDefault} $DISABLESPLASHSCREEN "$INIPATH\${NAME}.ini" "${NAME}" "DisableSplashScreen" "false"

		IfFileExists "$PROGRAMDIRECTORY\$PROGRAMEXECUTABLE" FoundProgramEXE NoProgramEXE

	NoINI:
		;=== No INI file, so we'll use the defaults
		StrCpy $PROGRAMEXECUTABLE "${DEFAULTEXE}"
		StrCpy $ADDITIONALPARAMETERS ""
		StrCpy $DISABLESPLASHSCREEN "false"

		IfFileExists "$EXEDIR\App\${DEFAULTAPPDIR}\${DEFAULTEXE}" "" NoProgramEXE
			StrCpy $PROGRAMDIRECTORY "$EXEDIR\App\${DEFAULTAPPDIR}"
			StrCpy $SETTINGSDIRECTORY "$EXEDIR\Data\${DEFAULTSETTINGSDIR}"
			Goto FoundProgramEXE

	NoProgramEXE:
		;=== Program executable not where expected
		StrCpy $MISSINGFILEORPATH $PROGRAMEXECUTABLE
		MessageBox MB_OK|MB_ICONEXCLAMATION `$(LauncherFileNotFound)`
		Goto TheEnd

	FoundProgramEXE:
		StrCmp $SECONDARYLAUNCH "true" GetPassedParameters
		FindProcDLL::FindProc "${DEFAULTEXE}"
		StrCmp $R0 "1" WarnAnotherInstance DisplaySplash

	WarnAnotherInstance:
		MessageBox MB_OK|MB_ICONINFORMATION `$(LauncherAlreadyRunning)`
		Goto TheEnd

	DisplaySplash:
		StrCmp $DISABLESPLASHSCREEN "true" CheckSettings
			;=== Show the splash screen before processing the files
			InitPluginsDir
			File /oname=$PLUGINSDIR\splash.jpg "${NAME}.jpg"
			newadvsplash::show /NOUNLOAD 1200 0 0 -1 /L "$PLUGINSDIR\splash.jpg"

	CheckSettings:
		;=== Check for data files
		IfFileExists "$SETTINGSDIRECTORY\*.*" GetPassedParameters

			;=== Create the default settings directory
			CreateDirectory "$SETTINGSDIRECTORY"

	GetPassedParameters:
		;=== Get any passed parameters
		${GetParameters} $0
		StrCmp "'$0'" "''" "" LaunchProgramParameters

		;=== No parameters
		StrCpy $EXECSTRING `"$PROGRAMDIRECTORY\$PROGRAMEXECUTABLE"`
		Goto AdditionalParameters

	LaunchProgramParameters:
		StrCpy $EXECSTRING `"$PROGRAMDIRECTORY\$PROGRAMEXECUTABLE" $0`

	AdditionalParameters:
		StrCmp $ADDITIONALPARAMETERS "" StartupCheck

		;=== Additional Parameters
		StrCpy $EXECSTRING `$EXECSTRING $ADDITIONALPARAMETERS`

	StartupCheck:
		StrCmp $SECONDARYLAUNCH "true" LaunchAndExit

	;GetPlatformLanguage:
		ReadEnvStr $0 "PortableApps.comLocaleWinName"
		StrCpy $APPLANGUAGE $0 "" 5
		StrCmp $APPLANGUAGE "" MoveSettings ;if not set, move on

	;FixPlatformLanguage:
		${IfThen} $APPLANGUAGE == PORTUGUESE ${|} StrCpy $APPLANGUAGE "Portugues (Portugal)" ${|}
		${IfThen} $APPLANGUAGE == PORTUGUESEBR ${|} StrCpy $APPLANGUAGE "Portugues (Brazilian)" ${|}
		${IfThen} $APPLANGUAGE == SIMPCHINESE ${|} StrCpy $APPLANGUAGE "Chinese (Simplified)" ${|}
		${IfThen} $APPLANGUAGE == TRADCHINESE ${|} StrCpy $APPLANGUAGE "Chinese(Traditional)" ${|}
		${IfThen} $APPLANGUAGE == SPANISH ${|} StrCpy $APPLANGUAGE "Espanol (America Latina)" ${|}

	;CheckAppLanguage:
		ReadINIStr $0 "$SETTINGSDIRECTORY\Medieval.reg" "Lang_Txt"
		StrCmp "$APPLANGUAGE" $0 RegistryBackup ;if the same, move on

	;SetAppLanguage:
		IfFileExists "$PROGRAMDIRECTORY\LANG\$APPLANGUAGE" "" RegistrySettings
		nsExec::Exec REG UPDATE $SETTINGSDIRECTORY\Medieval.reg "Lang_Txt" "$APPLANGUAGE"
		
	RegistryBackup:
		;=== Backup the registry
		${registry::KeyExists} "HKEY_CURRENT_USER\Software\Medieval-BackupBy${NAME}" $R0
		StrCmp $R0 "0" RestoreTheKey
		${registry::KeyExists} "HKEY_CURRENT_USER\Software\Medieval" $R0
		StrCmp $R0 "-1" RestoreTheKey
		${registry::MoveKey} "HKEY_CURRENT_USER\Software\Medieval" "HKEY_CURRENT_USER\Software\Medieval-BackupBy${NAME}" $R0
		Sleep 100
	
	RestoreTheKey:
		IfFileExists "$SETTINGSDIRECTORY\Medieval.reg" "" LaunchNow
	
		IfFileExists "$WINDIR\system32\reg.exe" "" RestoreTheKey9x
			nsExec::ExecToStack `"$WINDIR\system32\reg.exe" import "$SETTINGSDIRECTORY\Medieval.reg"`
			Pop $R0
			StrCmp $R0 '0' LaunchNow ;successfully restored key

	RestoreTheKey9x:
		${registry::RestoreKey} "$SETTINGSDIRECTORY\Medieval.reg" $R0
		StrCmp $R0 '0' LaunchNow ;successfully restored key
		StrCpy $FAILEDTORESTOREKEY "true"
	
	LaunchNow:
		Sleep 100
		ExecWait $EXECSTRING

	CheckRunning:
		Sleep 1000
		FindProcDLL::FindProc "${DEFAULTEXE}"                  
		StrCmp $R0 "1" CheckRunning
		
		StrCmp $FAILEDTORESTOREKEY "true" SetOriginalKeyBack
		${registry::SaveKey} "HKEY_CURRENT_USER\Software\Medieval" "$SETTINGSDIRECTORY\Medieval.reg" "" $0
		Sleep 100
	
	SetOriginalKeyBack:
		${registry::DeleteKey} "HKEY_CURRENT_USER\Software\Medieval" $R0
		Sleep 100
		${registry::KeyExists} "HKEY_CURRENT_USER\Software\Medieval-BackupBy${NAME}" $R0
		StrCmp $R0 "-1" TheEnd
		${registry::MoveKey} "HKEY_CURRENT_USER\Software\Medieval-BackupBy${NAME}" "HKEY_CURRENT_USER\Software\Medieval" $R0
		Sleep 100
		Goto TheEnd

	LaunchAndExit:
		Exec $EXECSTRING

	TheEnd:
		${registry::Unload}
		newadvsplash::stop /WAIT
SectionEnd