With Opus 11, a script is probably the best way to do it, if you want to preserve extensions with files (and not with folders).
Download this zip and extract the .orp (Opus Rename Preset) file inside it:
Various to spaces.zip (952 Bytes)
Then open the Rename dialog, and use File > Import to load the .orp file.
That should do what you want.
(This preset also works with Opus 12, of course.)
For reference, the script code which is inside the .orp file is also below.
This was based on a "Dots to Spaces" script I already had to hand, and it won't replace dots which are between numbers. So for example:
Hello.World.txt -> Hello World.txt
Directory-Opus_11.9-notes.txt -> Directory Opus 11.9 notes.txt
That's usually what you'd want, but if you want it to replace all dots, even ones in numbers, then it's a fairly simple change. Shout if you need help there.
Function Rename_GetNewName ( strFileName, strFullPath, fIsFolder, strOldName, ByRef strNewName )
' Create a RegExp object. See http://msdn2.microsoft.com/en-us/library/ms974570.aspx
Set re = new RegExp
re.IgnoreCase = True ' Case-insensitive matching.
re.Global = True ' All matches will be replaced, not just the first match.
' If we're renaming a file then remove the extension from the end and save it for later.
if fIsFolder or 0 = InStr(strFileName,".") then
strExtension = ""
strNameOnly = strFileName
strExtension = Right(strFileName, Len(strFileName)-(InStrRev(strFileName,".")-1))
strNameOnly = Left(strFileName, InStrRev(strFileName,".")-1)
' Apply our regular expression to the filename.
' This replaces dots, unless they are between numbers.
re.Pattern = "([^0-9])\.|\.([^0-9])"
strNameOnly = re.Replace(strNameOnly, "$1 $2")
' Also replace underscores and dashes with spaces.
re.Pattern = "[-_]"
strNameOnly = re.Replace(strNameOnly, " ")
' Rejoin the name and extension and we're finished
strNewName = strNameOnly & strExtension