Here is a tool that can help you do file manipulations like the ones you described.
If you open a command window, and type DO32 without parameters, you get this short help:

===========================================================
Usage : do /options <file spec> <command>
Substitutions:
 $=Full Path   #=Relative path
 @=File name   !=Path+Name (no changes)
 {=name        }=extension
 ?=Sequence number

Options :
 S        do subdirectories
 Q        prompted
 D        include only directory names
 E        do not echo line before executing
 Irhsa    include files with these attributes
 Xrhsa    exclude files with these attributes
 Adate    files >= this date
 Bdate    files <= this date
 Wca|b    as above, use windows create date
 Waa|b    as above, use windows access date
   dates can be DDMMYY or +-[n], where n is days from today
   if month or year in not specified, current month/year are used
 File spec : @name means read file list from <name>
             if name is blank, means standard input
 if command is blank, file names are echoed to standard output
===================================================================

let me try to explain what it does. The pseudo-language for the program would be :

FOR all files in list
 apply substitutions to the typed command
 execute result
NEXT

in other words, it executes the typed command for each file selected, using file name
substitutions.

as you see in the syntax, the option parameters are typed first, then the file specification,
then the command. It is always a good idea to enclose the command part in double quotes.
if the command itself needs to contain quotes (eg for long file names with spaces in them,
which need to be quoted), use single quotes around the command, and double quotes within the
command (or the other way around, I am not sure, test it).

Remember, you can always see that the program will do, and have a chance to cancel it,
by using the /Q option, which asks yes/no before doing anything.

Selecting files
===============
The file names that the program will operate on are selected in two ways:
 a. you can type a usual file pattern selection, like *.mp3  or a*g.doc
 b. you can supply a list of file names that is read from a text file
  (the second case allows you to specify files that have nothing in common in terms of name,
   or even reside in different directories)
   If you want to use syntax (b), precede the name of the file that contains the list with 
   an "@". example:
   do32 @list.txt command...
   
Operating on files
==================
it is important to understand that do32 itself does NOT do anything to the files. it is the
COMMAND that you type which does the work. so, in essense, do32 can do to a list of files
whatever can be done via command-line programs to files. in advanced usage, the list of "files"
may even NOT contain existing file names at all! (I will give an example later)


Options
=======
Options are useful only when you are selecting files from the file system via patterns, and NOT
when you are passing a list to the program. so, when you use the @ syntax, do not bother about
options

Metacharacters
==============
Metacharacters are used for macro substitution of parts of the file name specified. when
do32 processes a selected "file" name, it does the following substitutions:

 $=Full Path (only the directory part, not the filename)
 #=Relative path (same as above)
 @=File name   
 !=Path+Name (no change), equivalent to $@
 {=name        
 }=extension
 ?=Sequence number

so, given the file name :

C:\delphi7\utils\robot\html\personnel.htm

then,
$ = C:\delphi7\utils\robot\html\
@ = C:\delphi7\utils\robot\html\
! = C:\delphi7\utils\robot\html\personnel.htm
{ = personnel
} = .htm
? = 1..N, sequence number of selection

This is useful for constructing commands that operate on the file names, but need to change
some part of the filename:

Lets see some examples:

First, cases of selecting files via patterns:

*. null command. echoes the selection
 do32 *.* 
  Lists all files 
 do32 /s *.* 
  lists all files and all sub-directories of the current directory.
  
 do32 /s /a-5  *.*
  list all files that have been modified in the last 5 days in all subdrectories
  
 do32 /s /a010605 *.mp3  
  list mp3 files that have been modified after 01-june-2005 (note the date syntax: DDMMYY)
  dates can be relative to today also, by adding a + or - before the number of days.
  so /a-5 means 5 days ago, /a+0 means today, and /a+1 means tomorrow ("a"="after", there is also
  a "b" for "before")
  
 do32 /s /a+0 *.*
  list all files modified today
  
*. now lets see some commands applied on the selected files:

(I will not give any more examples of using options to select files. the above examples
should be enough. remember, you can use options with any of the examples, but NOT with the
"file list from text file" mode)

assuming that you have the following files in the current directory:
   a.txt
   b.txt

 do32 *.* "copy @ a:\@"
 
 will execute the following commands:
  copy a.txt a:\a.txt
  copy b.txt a:\b.txt
  
 do32 *.* "copy @ a:\{.bak"
  will execute the following commands:
    

  copy a.txt a:\a.bak
  copy b.txt a:\b.bak
  
At this point, you should say AAAA. you see, what the program does is to take each
file NAME (not actual file), apply parsing and then apply substitutions to the command, 
and then run the command. it is essentially a macro expander for file names and command-line
programs! what you can do with it is limited by your imagination.

let me give you a full example relative to what you want to do. lets say that you have a program
that can convert .wav files to .mp3 files from the command line, and it is called WAVTOMP3, but
the idiot programmer did not provide for naming the files corretcly. so, you have to type

wavtomp3 abcde.wav abcde.mp3

and cannot use wildcards, so this will not work : wavtomp3 *.wav *.mp3. here is how you do it
using DO32 :

do32 c:\source\*.wav "wavtomp3 ! d:\myMp3\output\@.mp3"

this will execute the program wavtomp3 for each file in the source dir, passing it the
appropriate parameter each time.

say that you have .ots files, and that you have an OTS2MP3 program that can convert them
back to mp3 (in fact I just looked in the web, a program like this DOES exist, it is called
MP3OTS.EXE, it is probably somewhere in your ots program directory, which may mean you do not need
to keep double copies in .ots and .mp3 format, to save some space. check it out)

this would do it:

do32 c:\lib\pap*.ots "OTS2MP3 ! c:\new\{.mp3"

now, to your specific need, which is quite complex, and a very good example of 
do32 capabilities:

say that you have a file LIST.TXT that contains a file list, like this:

c:\lib\a.ots
c:\lib\b.ots
... more like this, could even have directory paths

say also that you keep a copy of the music files in c:\libMP3, with the same relative paths.

the command you want in order to copy the corresponding mp3 files is :

do32 @list.txt "copy c:\libmp3\{.mp3 c:\dest"

so, the "{" extracts the filename without extension from the files in the list, which you then
use to "build" the source filename, by adding an .mp3 extension to it, then copy it to the 
destination. Easy, eh ? If you had sub-directories also, things could get a little complicated,
although it can still handle it.

if you wanted to use a DELETE list :

do32 @list.txt "del !"

move it to a new location, keeping same name:

do32 @list.txt "move ! c:\new\@"

move and rename at the same time:

do32 @list "move ! c:\new\{-new.ots"

etc etc