For renaming files in a folder in series, use the following code

Code:
Sub Renamer()

Const strPath As String = "C:\Path Of Folder\"

Dim strFile As String
Dim lngLoop As Long
lngLoop = 1
strFile = Dir(strPath)

Do While strFile <> ""
Name strPath & strFile As strPath & "ANYPREFIX" & Format(lngLoop, "0000") & Right(strFile, Len(strFile) - InStrRev(strFile, ".") + 1)
lngLoop = lngLoop + 1
strFile = Dir
Loop

End Sub