A simple windows batch script that will recompress .zip to .7z (depending on where 7-zip was installed, you may need to edit the paths):
@echo off
for %%F in (*.zip,*.rar) do ( "C:\Program Files\7-Zip\7z.exe" x -y -o"%%F_tmp" "%%F" * & pushd %%F_tmp & "C:\Program Files\7-Zip\7z.exe" a -y -r -t7z -mx9 -md1024m -mfb256 ..\"%%~nF".7z * & popd & rmdir /s /q "%%F_tmp" )
Or the following, which will automatically split the 7-zip into 2000000-byte chunks that can be directly attached to the post:
@echo off
for %%F in (*.zip,*.rar) do ( "C:\Program Files\7-Zip\7z.exe" x -y -o"%%F_tmp" "%%F" * & pushd %%F_tmp & "C:\Program Files\7-Zip\7z.exe" a -y -r -t7z -mx9 -md1024m -mfb256 -v2000000b ..\"%%~nF".7z * & popd & rmdir /s /q "%%F_tmp" )
BW-16D1HT | PX-W4824TU | PX-W5224A | PX-760A | PX-712A | Plextor Premium | Pioneer 209DBK | TS-H352C | TS-H353A | Wii