I started using this and found a problem. The data in the datarows is
converted but the datacolumn datatype stays as a byte array. If the dataset
is serialized for any reason (remoting was mine), there is an
invalidcastexception. Any suggestions on fixing this issue? I tried changing
the datacolumn.datatype but got an error that it can't be changed after the
dataset is created. In the mean time, I rewrote the function as follows:

Private Function Raw16ToGuid(ByRef dataSet As DataSet) As DataSet
           ' Creates a new dataset with GUID column and converted datatype
in place of byte arrays
           Dim table As DataTable
           Dim newDataSet As New DataSet
           For Each table In dataSet.Tables
               Dim newDataTable As New DataTable(table.TableName)
               Dim columnIndices As New ArrayList
               Dim dataColumn As DataColumn
               For Each dataColumn In table.Columns
                   If dataColumn.DataType Is
System.Type.GetType("System.Byte[]") Then
                       columnIndices.Add(dataColumn.Ordinal)
                       Dim newDataColumn As New
DataColumn(dataColumn.ColumnName, System.Type.GetType("System.Guid"))
                       newDataTable.Columns.Add(newDataColumn)
                   Else
                       Dim newDataColumn As New
DataColumn(dataColumn.ColumnName, dataColumn.DataType)
                       newDataTable.Columns.Add(newDataColumn)
                   End If
               Next
               Dim dataRow As DataRow
               For Each dataRow In table.Rows
                   Dim index As Integer = 0
                   Dim newDataRow As DataRow = newDataTable.NewRow
                   For Each item As Object In dataRow.ItemArray
                       If columnIndices.Contains(index) Then
                           newDataRow(index) = New Guid(CType(item,
Byte())) ' convert guid
                       Else
                           newDataRow(index) = item
                       End If
                       index += 1
                   Next
                   newDataTable.Rows.Add(newDataRow)
               Next
               newDataSet.Tables.Add(newDataTable)
           Next
           Return newDataSet
       End Function

This creates a new dataset with the row translated. I am sure this is less
efficient but I can't find a way to cleanly translate the datatype in place.
Thanks for any feedback.