Batch rename issue when dealing with special characters in the filename

I have several hundred *.mp3 files in c:\files. There are all imaginable filenames in there like

milad.mp3 (good behaving)
hey you.mp3 (space in filename)
systemofadown.mp3 (long filename)
howdy(1).mp3 (parentheses in filename)

and any combination of the last three conditions. I want to rename the files to 001-test.mp3, 002-mp3, ... It doesn't matter which file gets which name. have written a batch file to do the rename. Here is my code (with line numbers added):

01  rem @echo off
02  cls
03  set _number=%1
04  lfnfor on
05
06  :F1TO10
07  IF NOT EXIST *.mp3. goto end
08  if %_number% gtr 9 goto F10TO100
09  for /f %%a IN ('dir /b *.mp3') do rename %%~na.mp3 00%_number%-test.mp4
10  set /a _number +=1
11  goto F1TO10
12
13  :F10TO100
14  IF NOT EXIST *.mp3. goto end
15  if %_number% gtr 99 goto F100TO1000
16  for /f %%a IN ('dir /b *.mp3') do rename %%~na.mp3 0%_number%-test.mp4
17  set /a _number +=1
18  goto F10TO100
19
20  :F100TO1000
21  IF NOT EXIST *.mp3. goto end
22  if %_number% gtr 999 goto end
23  for /f %%a IN ('dir /b *.mp3') do rename %%~na.mp3 %_number%-test.mp4
24  set /a _number +=1
25  goto F100TO1000
26
27  :end
28  for /f %%a IN ('dir /b *.mp4') do rename %%~na.mp4 %%~na.mp3
29  echo Done

This code works fine for good behaving filenames (i.e. no spaces, no parentheses, no longer than 8 chars long). But if I have even a single file with a bad behaving filename, the script breaks (it loops endlessly until I stop it with Ctrl-C).

The problem is obviously a filename issue. How can this be fixed? Any ideas? I'd greatly appreciate any help.

Solution

First of all I would like to thank the friends who offered help through answers. But none was what I was looking for. Actually I arrived at a flawlessly working script using help provided by Spire posted as an answer to this question.

Here is the final code: (no need for line numbers this time)

rem @echo off
cls
set _number=%1

:F1TO10
IF NOT EXIST *.mp3. goto end
if %_number% gtr 9 goto F10TO100
for /f "usebackq delims=" %%x in (`dir /b *.mp3`) do rename %%~nsx.mp3 00%_number%-test.mp9
set /a _number +=1
goto F1TO10

:F10TO100
IF NOT EXIST *.mp3. goto end
if %_number% gtr 99 goto F100TO1000
for /f "usebackq delims=" %%x in (`dir /b *.mp3`) do rename %%~nsx.mp3 0%_number%-test.mp9
set /a _number +=1
goto F10TO100

:F100TO1000
IF NOT EXIST *.mp3. goto end
if %_number% gtr 999 goto end
for /f "usebackq delims=" %%x in (`dir /b *.mp3`) do rename %%~nsx.mp3 %_number%-test.mp9
set /a _number +=1
goto F100TO1000

:end
for /f %%a IN ('dir /b *.mp9') do rename %%~na.mp9 %%~na.mp3
echo Done.