I installed some texture mods and looked at the solutions to getting them to appear and it seemed like "ArchiveInvalidationInvalidated!.bsa" (from TES Nexus) was the simplest. I must be doing something wrong though because it does not work and I still get the old textures. I placed the .bsa file in /Data/ and in Oblivion.ini. Is there an extra step I am missing? I have the Steam version and am running Windows 7.

You need to register the BSA in your Oblivion.INI in the Documents\My Games\Oblivion directory. Go there, find the entry sArchiveList, and add ArchiveInvalidationInvalidated!.bsa to the list with a comma and a space at the end.

That's what I did. I think.

Here's what I tried:

SArchiveList=ArchiveInvalidationInvalidated!.bsa, Oblivion - Meshes.bsa, Oblivion - Textures - Compressed.bsa, Oblivion - Sounds.bsa, Oblivion - Voices1.bsa, Oblivion - Voices2.bsa, Oblivion - Misc.bsa

SArchiveList=Oblivion - Meshes.bsa, ArchiveInvalidationInvalidated!.bsa, Oblivion - Textures - Compressed.bsa, Oblivion - Sounds.bsa, Oblivion - Voices1.bsa, Oblivion - Voices2.bsa, Oblivion - Misc.bsa

SArchiveList=Oblivion - Meshes.bsa, Oblivion - Textures - Compressed.bsa, Oblivion - Sounds.bsa, Oblivion - Voices1.bsa, Oblivion - Voices2.bsa, Oblivion - Misc.bsa, ArchiveInvalidationInvalidated!.bsa

None of these worked.

You need to do several edits for it to work.
First I assume you placed the .bsa file inside your data folder right?
Then you need to edit the oblivion.ini file found inside my games > oblivion. You already did that I see, and your second attempt was the most correct one
Then you need to edit the oblivion_defailt.ini found inside yout oblivion folder (it's next to your data folder but not inside it!)

To make the process much more painless, why don't you use the installer version of archiveinvalidation_invalidated? It's automatic and works flawlessly,

Yes the installer version would be easier, but I would like to know what exactly is going on.

What in the oblivion_default.ini do I edit? It doesn't have an sArchiveList entry, and when I added on in it didn't do anything. Also, the readme doesn't mention this.