I tested these 2 batch files on my XP system against my project folder and it worked.
Batch file 1 - update to point to correct path - run this file after saving both batch files. I would save this one as doit.bat:
for /f "tokens=*" %%a IN ('dir /b /s "c:\temp\myrootcodefolder\*.*"') do call allmycode.bat %%a %%~xa
Batch file 2 - Update to include any extensions you need that I didn't list. Be sure to save as allmycode.bat
if %2.==. goto :END
if %2==.vb goto :OUTPUT
if %2==.cs goto :OUTPUT
if %2==.aspx goto :OUTPUT
if %2==.txt goto :OUTPUT
if %2==.config goto :OUTPUT
if %2==.asax goto :OUTPUT
if %2==.asmx goto :OUTPUT
if %2==.skin goto :OUTPUT
GOTO :END
:OUTPUT
echo. >> allmycode.txt
echo. >> allmycode.txt
echo ============================================ %1 >> allmycode.txt
echo. >> allmycode.txt
type %1 >> allmycode.txt
:END