I have been collecting more values for TaskBarWinXP and have to review the previous script. For all these values, the QuickLaunch Taskbar was disabled:
 Code:
0c000000080000000200000000000000aa4f2868486ad0118c7800c04fd918b4b7020000600d0000000000001e00000000000000000000001e0000000000000001000000010000008b8a0d543f1c324e8132530f6a5020901d00000060050000000000001c00000000000000000000001c0000000000000001000000
0c000000080000000200000000000000aa4f2868486ad0118c7800c04fd918b4db020000600d0000000000001e00000000000000000000001e0000000000000001000000010000008b8a0d543f1c324e8132530f6a5020901d00000060050000000000001c00000000000000000000001c0000000000000001000000
0c000000080000000200000000000000aa4f2868486ad0118c7800c04fd918b4c9030000600d0000000000001e00000000000000000000001e0000000000000001000000010000008b8a0d543f1c324e8132530f6a5020901d00000060050000000000001c00000000000000000000001c0000000000000001000000
0c000000080000000200000000000000aa4f2868486ad0118c7800c04fd918b4c9020000600d0000000000001e00000000000000000000001e0000000000000001000000010000008b8a0d543f1c324e8132530f6a5020901d00000060050000000000001c00000000000000000000001c0000000000000001000000
0c000000080000000200000000000000aa4f2868486ad0118c7800c04fd918b4ff030000600d0000000000001e00000000000000000000001e0000000000000001000000010000008b8a0d543f1c324e8132530f6a5020901d00000060050000000000001c00000000000000000000001c0000000000000001000000
0c000000080000000200000000000000aa4f2868486ad0118c7800c04fd918b4ed030000600d0000000000001e00000000000000000000001e0000000000000001000000010000008b8a0d543f1c324e8132530f6a5020901d00000060050000000000001c00000000000000000000001c0000000000000001000000
0c000000080000000200000000000000aa4f2868486ad0118c7800c04fd918b455030000600d0000000000001e00000000000000000000001e0000000000000001000000010000008b8a0d543f1c324e8132530f6a5020901d00000060050000000000001c00000000000000000000001c0000000000000001000000
0c000000080000000200000000000000aa4f2868486ad0118c7800c04fd918b455030000600d0000000000001e00000000000000000000001e0000000000000001000000010000008b8a0d543f1c324e8132530f6a5020901d00000060050000000000001c00000000000000000000001c0000000000000001000000
0c000000080000000100000000000000aa4f2868486ad0118c7800c04fd918b477030000e00c0000000000001e00000000000000000000001e0000000000000001000000
0c000000080000000200000000000000aa4f2868486ad0118c7800c04fd918b45d030000600d0000000000001e00000000000000000000001e0000000000000001000000010000008b8a0d543f1c324e8132530f6a5020902d00000060050000000000001c00000000000000000000001c0000000000000001000000
0c000000080000000200000000000000aa4f2868486ad0118c7800c04fd918b466030000600d0000000000001e00000000000000000000001e0000000000000001000000010000008b8a0d543f1c324e8132530f6a5020901400000060050000000000001c00000000000000000000001c0000000000000001000000
0c000000080000000200000000000000aa4f2868486ad0118c7800c04fd918b4cb030000600d0000000000001e00000000000000000000001e0000000000000001000000010000008b8a0d543f1c324e8132530f6a5020902d00000060050000000000001c00000000000000000000001c0000000000000001000000
0c000000080000000200000000000000aa4f2868486ad0118c7800c04fd918b493030000600d0000000000001e00000000000000000000001e0000000000000001000000010000008b8a0d543f1c324e8132530f6a5020902d00000060050000000000001c00000000000000000000001c0000000000000001000000
0c000000080000000200000000000000aa4f2868486ad0118c7800c04fd918b481030000600d0000000000001e00000000000000000000001e0000000000000001000000010000008b8a0d543f1c324e8132530f6a5020902d00000060050000000000001c00000000000000000000001c0000000000000001000000

I think checking for the existance and the length of the value should be enough to avoid that double and triple QuickLaunch Taskbars get created.
;*************************************************************************
; Script Name: EnableQLToolbar
; Author: Wim Rotty
; Date: 2008/9/11
; Description: Enable Quick Launch Toolbar only if it is disabled
;*************************************************************************

;;;;;;;;;;;;;;;;;;
; Script Options ;
;;;;;;;;;;;;;;;;;;

If Not @LOGONMODE
    Break On
Else
    Break Off
EndIf
Dim $RC
$RC = SetOption("Explicit", "On")
$RC = SetOption("NoMacrosInStrings", "On")
$RC = SetOption("NoVarsInStrings", "On")
If @SCRIPTEXE = "KIX32.EXE"
    $RC = SetOption("WrapAtEOL", "On")
EndIf

;;;;;;;;;;;;;;;;;;;;;
; Declare variables ;
;;;;;;;;;;;;;;;;;;;;;

DIM $TaskbarWinXP

;;;;;;;;
; Code ;
;;;;;;;;

; -- QL: Enable Quick Launch Toolbar
; Check if OS is Windows XP
If @DOS = "5.1"
    ; $TaskbarWinXP = ReadValue('HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Streams\Desktop','TaskbarWinXP')
    $TaskbarWinXP = ReadValue('HKEY_USERS\'+@SID+'\Software\Microsoft\Windows\CurrentVersion\Explorer\Streams\Desktop','TaskbarWinXP')
    ; Check if Quick Launch Toolbar is disabled
    If
    ; Check if RegName TaskbarWinXP exists
    @ERROR<>0
    Or
    ; Check if the Value for TaskbarWinXP is at least 248 chars long
    Len($TaskbarWinXP)<=248
        ; ? "Disabled"
        Shell '"%ComSpec%" /C "'+@LSERVER+'\NETLOGON\toggleql.exe" 1'
    ; Else
        ; ? "Enabled"
    EndIf
EndIf