IE Changes EPS to PS Files when Downloading
If you plan to link directly to an .EPS or .AI file for downloading (e.g. logos, vector art, etc.) on a website, you should note that Internet Explorer (IE6 & IE7) doesn’t correctly handle these postscript files. If you attempt to download an .eps file with IE it will save it as a .ps file and it will save an .ai file as a .pdf. This is not a problem in Firefox or Opera.
The simple solution is to zip these types of files so IE doesn’t change the file extension, and your visitors can download them without problems.