zachturner009 - If you're responding to someone other than the Original Poster (OP) then it is best to use the mention feature or quote feature so that they know to respond to you. To use the mention just type the @ symbol and start typing the person's name without any spaces. After a couple letters some suggestions will come up and just click the one you want.
Zach, are you having trouble with the zip files on this site or the old site? I just downloaded the Halo 3 ODST files that we currently have in the armory here and had no issues opening it. I'm not sure what program you are using, but WinRAR is a free program and works well for unzipping numerous file types. Good luck! Feel free to message me if you continue to have issues.
If you would like people to help you, you do need to be a little more specific and give more information. Which version of the ODST armor are you looking for? Which files did you download and what issue exactly did you have?
All the files in the Armory are zipped. As PerniciousDuke you need to unextract or unzip them using a program like WinRar to access them. Did you attempt to unzip files before you had issues?
I also just downloaded some of the zipped ODST files from the Armory, on Fire Fox, and accessed them with a different free program, 7-Zip, and had no issue.
Here are the different ODST variants, by game. The most difficult ones there are likely gonna be 3, Buck, or Nightfall. But I'm not sure if there are variants for all of these in the armor repository. I kinda want to go for a Halo 4 ODST myself. Here's a tutorial that should go over the basics of making a set, though it is incomplete.