I have tribunal and bloodmoon working, i have copied all the files and everything like that, but whenever I go into Dura Gra Bol's house, an error message comes up saying that a texture won't load, "A_netch_cuirass.nif" it is on Dura Gra Bol herself, but when I choose 'yes' to continue running the executable and go see her, she's a giant yellow shape with a blue exclamation point, is there any way to fix this error? I never had this error before I installed the expansions

Read the http://www.gamesas.com/index.php?/topic/781497-vistawindows-7-problems/ for Vista/Windows7 problems.
This is a similar error as the Snowflake Error, but for Tribunal instead of Bloodmoon.

But, much simpler to do, is just change the install location of the game. (details in the pinned thread above)