Was trying to help out a co-worker with adjusting a macro but I'm at a loss.

The macro below sorts through POs and creates and individual file for each PO to be sent to the vendor. The problem we are having is when the files get sent over, the vendors are on excel 2003 and can't open the files. My co-worker just got upgraded to 2010 which is when the problem started. Her default settings have been adjusted to save out files as a 97-2003 workbook and you can see the macro names the files .xls. They look fine after they are saved, but when you try to open them, it says the "workbook is in a different format than the extension" and if you say its fine, opens it as a .xlsx file.

Any thoughts?

Sub SaveWS_to_NewWBs()
Dim wb As Workbook
Dim ws As Worksheet
Dim B As Variant
B = Range("C8").Value
For Each ws In ThisWorkbook.Worksheets
    ws.Copy
    Set wb = ActiveWorkbook
    wb.SaveAs ThisWorkbook.Path & "\" & ws.Range("A8").Value & " " & ws.Name & " " & ws.Range("X8").Value & " " & Format(B, "yyyymmdd") & ".xls"
    wb.Close False
Next ws
End Sub