Meh I can't guarantee this will work as I only did a quick test on my own computer before posting.
[highlight=vb.net]
Private Function getDefaultBrowser() As String
Dim retVal As String = String.Empty
Using basekey As Microsoft.Win32.RegistryKey = My.Computer.Registry.ClassesRoot.OpenSubKey(".html ", False)
retVal = basekey.GetValue("").ToString.Replace("HTML", "")
End Using
Return retVal
End Function
[/highlight]
Yeah, try that out.