Once you've "Activated" ArchiveInvalidation Invalidated! you do not need to keep it running to receive its effects or activate it again when adding/removing textures ect.
-ArchiveInvalidation Invalidated! will set bInvalidateOlderFiles to 1, on some computers setting bInvalidateOlderFiles to 1 in Fallout 3's ini will cause the game to crash on startup, at the moment it is unknown why this happens and there is no solution yet, unfortunatly you'll have to do without ANY modified original content since bInvalidateOlderFiles needs to be set to 1 to use any.
If you are using Windows Vista make sure you DO NOT play Fallout 3 from your Program Files folder, this has been known to cause strange problems (if UAC is on/incorrect permissions), install Fallout 3 somewhere else.
-This will work with all versions of Fallout 3.
-ArchiveInvalidation Invalidated! will set bLoadFaceGenHeadEGTFiles to 1 as well which allows new NPC's added by a mod to have their proper body/face color as they where set in G.E.C.K.
-ArchiveInvalidation Invalidated! can be run from anywhere, it will read your Fallout 3 path from the registry and if it cannot find it/path is incorrect it will ask you to choose your Fallout 3 folder.
-ArchiveInvalidation Invalidated! will delete your ArchiveInvalidation.txt upon activation, keeping ArchiveInvalidation.txt while ArchiveInvalidation Invalidated! is active can cause issues.