Problems downloading Zip files from SharePoint

We had some problems with our SharePoint (on SBS2008) with Zip files.  Users could upload the files fine, but when trying to access them it would say:

Cannot open file: it does not appear to be a valid archive. If you downloaded this file, try downloading the file again.

We found the problem was that IIS had compression turned on and was gzipping the Zip file a second time.  Following the instructions at we solved it by changing the MIME type of Zip to application/octet-stream.  The steps were as follows:

  1. Click on Start, point to Administrative Tools, and then click on Internet Information Services (IIS) Manager.
  2. Right-click on the server (local computer) tree, where server (local computer) is the name of your IIS server, and then click on Properties.
  3. Click on MIME Types.
  4. Scroll down to the registered MIME type list to find the .zip entry.
  5. Click on the .zip application/x-zip-compressed entry, and then click Edit.
  6. Modify the MIME type value to application/octet-stream.
  7. Then Stop and then restart the IIS Admin Service to apply the change to the MIME type.