|Yeh, you're right, FOR /R is made to do that:|
@echo off & setlocal
for /r %%a in (audit_*.*) do ren %%~pnxa qrep_%%~nxa
You can also use FOR /F like:
for /f %%a in ('dir /b /s audit_*.*') do ren %%a qrep_%%~nxa
You might want to test with a small test-set before unleashing the beast, although I did test in on my end and it worked ok (I've hardly ever used FOR /R, so I had to trial/error till I got it right).