If you look at most Poser downloads, you'll find the ZIP file is set up so that it includes folders starting at Runtime. This is because people can choose to install their copy of Poser on different drives, and there are other possible differences in the path (Poser3 vs. Poser4, Metacreations vs. Curious Labs, etc.). The easiest way is to create a separate directory called Runtime in the root of your drive, followed by the usual Poser directory structure. Then copy the stuff that's going to be in your download to the appropriate places in these folders. Then just Zip it up with "include subdirectories" selected, or whatever your zip program calls it.