ok when ever i try to add a house mod it simply doesnt show.... for example im trying to add
Bas Leijser's arena house mod v2 and the portal wont show up frankly i dont think it's even loading.

i am running windows xp, oldblivion, oblvion patch 1.2 (but it wont work with out the video fix exe otherwise crashes at menu... so on menu is say 1.0.2. i think i need video fix exe ver 1.2 but cant find)

Do you have Sivering Isles installed? If not, make sure the housemod you're using doesn't require SI to be installed on your machine.
Then uh... try Oblivion Mod Manager and sort your mods a little bit. Sometimes it helps to load some mods last (move it down in the list)
You might also need OBSE for some mods, make sure it is installed too - and if you use OBMM it will load OBSE automatically if it is installed.
Then make sure to have all stuff in their right directories...

If you got that all and it still won't work and you're sure that it is not the mod itself I suggest to re-install the game. ^^"