How do you strip quotes out of an ECHO'ed string in a Windows batch file?

I have a Windows batch file I'm creating, but I have to ECHO a large complex string, so I'm having to put double quotes on either end. The problem is that the quotes are also being ECHOed to the file I'm writing it to. How do you ECHO a string like that and strip the quotes off?

UPDATE:

I've spent the last two days working on this and finally was able to kludge something together. Richard's answer worked to strip the quotes, but even when I put the ECHO in the subroutine and directly outputted the string, Windows still got hung up on the chars in the string. I'll accept Richard's answer since it answers the question asked.

I ended up using Greg's sed solution, but had to modify it because of sed/windows bugs/features (it didn't help that it came with no documentation). There are a few caveats to using sed in Windows: you have to use double quotes instead of single quotes, you can't escape the double quotes in the string directly, you have to endquote the string, escape using the ^ (so ^") then beqin quote for the next section. Also, someone pointed out that if you pipe input to sed, there's a bug with a pipe being in the string (I didn't get to verify this since in my final solution, I just found a way not to have all quotes in the middle of the string, and just removed all quotes, I never could get the endquote to be removed by itself.) Thanks for all the help.

Solution

The call command has this functionality built in. To quote the help for call:

 Substitution of batch parameters (%n) has been enhanced.  You can
 now use the following optional syntax:

 %~1         - expands %1 removing any surrounding quotes (")

Here is a primitive example:

@echo off
setlocal
set mystring="this is some quoted text"
echo mystring=%mystring%
call :dequote %mystring%
echo ret=%ret%
endlocal
goto :eof

:dequote
setlocal
rem The tilde in the next line is the really important bit.
set thestring=%~1
endlocal&set ret=%thestring%
goto :eof

Output:

C:\>dequote
mystring="this is some quoted text"
ret=this is some quoted text

I should credit the 'environment variable tunneling' technique (endlocal&set ret=%thestring%) to Tim Hill, 'Windows NT Shell Scripting'. This is the only book I have ever found that addresses batch files with any depth.