While i've modded Morrowind before, I have never really used texture replacer mods, and so I decided recently to try some out. The problem is, when I install pluginless replacers none of the textures show up.

For example, if I use Lougian's Landscape Retexture mod, and install it just as it says, putting the texture folder into Data Files, when I start up the game, the same vanilla textures appear.

And so i'm wondering what it is I am doing wrong.

From what I can tell, it is either because I have the steam version of the game, or something involving BSAs

Any help would be appreciated, as I obviously have no idea what I'm doing.

Scroll down here: http://www.gamesas.com/topic/1305729-mod-recommendations-for-new-players/

There's a section of info for Steam users which addresses your problem.
Also relevant info if you're on Vista or WIn7-8