Before doing the following make sure you save a copy of your save game files and copies of the files that you are editing for that JUST IN CASE situation
1) Download the manual version of ArchiveInvalidation Invalidated http://www.fallout3nexus.com/downloads/file.php?id=944 (make sure it is the manual version and not the recommended) and place the .bsa file in your [location of steam]\steamapps\common\Fallout New Vegas\Data folder
2) Open the following files on your computer in notepad or something similar:
\steamapps\common\Fallout New Vegas\fallout_default.ini
My Documents\My Games\Fallout NV\falloutprefs.ini
My Documents\My Games\Fallout NV\fallout.ini
(fallout.ini may be read only, right click on the file and choose properties, uncheck read only and hit apply. After making the changes below, put fallout.ini back to read only)
3) Edit the [Archive] section in each file
Make the SArchiveList look like:
SArchiveList=ArchiveInvalidationInvalidated!.bsa, Fallout - Textures.bsa, Fallout - Textures2.bsa, Fallout - Meshes.bsa, Fallout - Voices1.bsa, Fallout - Sound.bsa, Fallout - Misc.bsa
Save and close the file (make sure you put fallout.ini back to read only)