Mass file extension changing

I have about 1000 files that I need to change the file extension on. They are all the same now and need to be changed to the same extension (in this case they are being changed from *.m4a to *.m4b.

How can I change them all at once using whatever. I really don't care if it is in windows or a mac/unix (I could do it on my pc or my ibook).

Open a command prompt (Start | Run | Type cmd, and click OK | At the C:\> prompt (assuming the files are located in the root directory. If they're not, then just change the path to the files accordingly using the CD command), then type...

C:\>REN *.M4A *.M4B

For example, when you open the command prompt, you're greeted with...

C:\Documents and Settings\Your Name\>

If for example the files are located on the Desktop, CD to the Desktop directory using the cd desktop command. You should then see...

C:\Documents and Settings\Your Name\Desktop>

You can then type...

REN *.M4A *.M4B and ENTER

sweet. that worked great. Thanks

woah. that would have saved me alot of time a while ago.
il remember this.

There is actually a backwards way to do it in win2k and xp, but I forget how. And it isn't as powerful as good ol dos.

Wish I know that earlier. I thought batch changing file extensions is not possible and changed 40+ file extensions manually . pathetic. used this here