Why do my Office 2007 files appears as Zip files in Vista ?
Microsoft Office 2007 introduces a new file format for Microsoft Office Word, Microsoft Office Excel, and Microsoft Office PowerPoint files. The new file format is XML-based and automatically compresses when saved and decompresses when opened using zip compression technology. New file name extensions are included with these new file formats. As a result, Microsoft Office Word files which were appended with .doc are now, in general, appended with .docx. There are also further file formats that represent templates and, for security reasons, clearly identify files that rely on Visual Basic macros. For the most part, users will be working with the .docx extension.
The new file name extensions are not currently supported in Vista. As a result of the unrecognized file name extension and the use of zip compression technology, Microsoft Office 2007 files that are uploaded to Vista appear with a .ZIP file name extension instead of the appropriate Microsoft Office 2007 file name extension.
Blackboard is actively working on updates that will support the new Microsoft Office 2007 file types. In the meantime, users should save files in the earlier, Microsoft Office 2003 file format instead of the new, XML file type before uploading to Vista. To do so, simply use the Save As function in Microsoft Office and select the earlier file type: .doc for Microsoft Office Word files, .xls for Microsoft Office Excel files, and .ppt for Microsoft Office PowerPoint files. ( See the Office 2007 Tutorials for instructions on saving files in the compatible format.)
For more information on the new file types in Microsoft Office 2007, please see http://office.microsoft.com/en-us/help/HA100069351033.asp