Halo Patch Installation - Needs admin privalages?

[Sprtn-005]

i install halo again because my game blacks out when it starts up. That's fixed now, but then when i try to play online it says i need a patch. i say ok, and it starts to install, but says i need to be a user with admin!! I AM on my computer. (The only 1!) and then i already had the patch from before, and it says (when i try to install manually) u msut have halo installed to install patch. so i put in my halo cd in again and it says not "play halo" but "install halo"!!! I can play halo still, but not online for some reason i CAN play halo CE online though. sum1 help