Bad word filter

[blindlizard]

Does anyone know how to make a bad word filter that is case insinsitive? I have been google-ing all night and found some different examples of word filters (some better than others), but none that are case insensitive without changing the case of the text. I basically want to do what this forum does without having to add diferent cases to the words. Like lets say crap is a bad word, I want it to find Crap, crAP, CRAP, etc, but not crape. I know it can be done with regular expressions (which I think this board uses) but I don't know regular expressions worth crap. Here is the code I have now, but it is case sensative:

Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Dim xmlDocPath As String = Server.MapPath("bad_words.xml")
        Dim xmlReader As XmlTextReader = New XmlTextReader(xmlDocPath)
        While (xmlReader.Read())
            If xmlReader.NodeType = XmlNodeType.Text Then
                alWordList.Add(xmlReader.Value)
                Trace.Write("Added: " & xmlReader.Value)
            End If
        End While
        xmlReader.Close()
    End Sub
 
    Public Function CheckString(ByVal InputString As String) As String
        Dim r As Regex
        Dim element As String
        Dim output As String
        Trace.Write("Checking " & InputString)
        For Each element In alWordList
            r = New Regex("\b" & element)
            Trace.Write("Checking: " & element)
            InputString = r.Replace(InputString, "****")
        Next
        Trace.Write("Returning " & InputString)
        Return InputString
    End Function
 
 
XML
<words>
    <word>badword</word>
    <word>reallybadword</word>
    <word>omgyouusedthisword</word>
</words>