filenames - Make every file in a Directory Structure Lowercase (Windows)

I have a legacy directory structure from a desktop application that I'm porting to an Android application, and Android doesn't want the names of the files to have capital letters in them. I had originally decided to suck it up and rename them by hand (about a hundred files), but then I found that Windows was thwarting even those attempts: QuotationMarks.png -> quotationmarks.png doesn't even stick, because Windows is case-insensitive: it doesn't even register it is as a filename change. I'd have to QuotationMarks.png -> quotationmarks2.png -> quotationmarks.png for all files, which I would like to avoid.

So is there some kind of secret power app that will allow to perform this operation batch?

Answer

Command line:

for /F %a in ('dir /L /B') do ren %a %a

batch:

for /F %%a in ('dir /L /B') do rename %%a %%a