"With some mods, you might POSSIBLY have these folders:
Video
Music
Sound
LSData
Menus
Shaders
Select all of these items -- except ArchiveInvalidation.txt, which we'll deal with in a minute -- and copy/paste or drag them into your Oblivion "Data" folder (described in Step 1 above).
If you already have some of these folders, Windows will prompt you with a warning about files with the same name. Click "Yes to All". "
Many users may actually try to overwrite the entire folders instead of just replacing the files within them which can lead to many problems. For example, if a mod only replaces "Battlebattle_01.mp3" in the "\Data\Music\" folder and you simply drag the modder's "\Data\Music\" folder over to your data folder, you would end up overwriting the original "\Data\Music\" folder which contains 8 tracks "Battlebattle_01.mp3 - Battlebattle_08.mp3" with the modder's folder that only contains 1 track. I suggest you specify not to do folder replacements but file replacements instead. It's more time consuming but a user can ensure that they will only be replacing the files that need to be replaced and that they will not be accidentally deleting any un-modded files. This also allows the user to back up or rename only the files that are going to modded if hard drive space is an issue.
You're mistaken about how Windows does folder "replace". It says:
"If the files in the existing folder have the same name as files in the folder you are moving or copying, they will be replaced."