I couldn't find any mention of this type of problem here so I'm sure it is something on my end but I was hoping someone might understand what's happening. I get this error after I install Quest 5.1.1 and try to launch it.

System.InvalidOperationException: An error occurred creating the form. See Exception.InnerException for details.  The error is: Parameter is not valid. ---> System.ArgumentException: Parameter is not valid.
   at System.Drawing.Font.GetHeight(Graphics graphics)
   at System.Drawing.Font.get_SizeInPoints()
   at System.Drawing.SystemFonts.FontInPoints(Font font)
   at System.Drawing.SystemFonts.get_MenuFont()
   at System.Windows.Forms.ToolStripManager.get_DefaultFont()
   at System.Windows.Forms.ToolStripItem.get_Font()
   at System.Windows.Forms.ToolStripItemInternalLayout.CommonLayoutOptions()
   at System.Windows.Forms.ToolStripDropDownButton.ToolStripDropDownButtonInternalLayout.CommonLayoutOptions()
   at System.Windows.Forms.ToolStripItemInternalLayout.GetLayoutData()
   at System.Windows.Forms.ToolStripItemInternalLayout.PerformLayout()
   at System.Windows.Forms.ToolStripItem.OnBoundsChanged()
   at System.Windows.Forms.ToolStripDropDownItem.OnBoundsChanged()
   at System.Windows.Forms.ToolStripItem.SetBounds(Rectangle bounds)
   at System.Windows.Forms.ToolStripOverflowButton.SetBounds(Rectangle bounds)
   at System.Windows.Forms.ToolStripItem.set_Size(Size value)
   at System.Windows.Forms.ToolStrip.get_OverflowButton()
   at System.Windows.Forms.ToolStripSplitStackLayout.get_OverflowButtonSize()
   at System.Windows.Forms.ToolStripSplitStackLayout.LayoutHorizontal()
   at System.Windows.Forms.ToolStripSplitStackLayout.LayoutCore(IArrangedElement container, LayoutEventArgs layoutEventArgs)
   at System.Windows.Forms.Layout.LayoutEngine.Layout(Object container, LayoutEventArgs layoutEventArgs)
   at System.Windows.Forms.Control.OnLayout(LayoutEventArgs levent)
   at System.Windows.Forms.ScrollableControl.OnLayout(LayoutEventArgs levent)
   at System.Windows.Forms.ToolStrip.OnLayout(LayoutEventArgs e)
   at System.Windows.Forms.Control.PerformLayout(LayoutEventArgs args)
   at System.Windows.Forms.Control.PerformLayout()
   at System.Windows.Forms.Control.ResumeLayout(Boolean performLayout)
   at System.Windows.Forms.ToolStrip..ctor()
   at AxeSoftware.Quest.ElementList.InitializeComponent()
   at AxeSoftware.Quest.ElementList..ctor()
   at AxeSoftware.Quest.Player.InitializeComponent()
   at AxeSoftware.Quest.Player..ctor()
   at AxeSoftware.Quest.Main.InitializeComponent()
   at AxeSoftware.Quest.Main..ctor()
   --- End of inner exception stack trace ---
   at AxeSoftware.Quest.My.MyProject.MyForms.Create__Instance__[T](T Instance)
   at AxeSoftware.Quest.My.MyApplication.OnCreateMainForm()
   at Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.OnRun()
   at Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.DoApplicationModel()

The only odd thing that happened during install is the .net download hangs up and I wound up cancelling and downloading it separately from MS. I have tried to reinstall/repair the .net framework and it seems to be installed correctly although I don't know another way to test it. I have also reinstalled Quest and a slightly older version but none have worked. I have Quest installed on my Vista laptop and it's been working wonderfully. Thank you.

Windows XP SP3
.net Framework v4.0.30319

Maybe you're missing some system fonts in your XP installation?

It was something like that, I checked and the fonts seemed to be there. Then I changed my XP theme to Windows Classic (it was the Windows Zune theme) and it worked. Thank you.