Could you post the error message you get? If you get one....it sounds like a compatability problem. I would take a look at this update, and see if maybe you need it, Im not the most tech savy to know if it would be what does work.
Download details: Microsoft Office Compatibility Pack for Word, Excel, and PowerPoint 2007 File Formats
Best of luck to you
Are you running Microsoft Office 2007??
If so, to open, save, or read Office 2007 file formats (Word=XML Powerpoint=Powerpoint 2007 Presentation Excel=Excel 2007 Workbook or XML) You do need to install the compatibility Pack noted in the above post.
This works for opening 2003 documents in 2007 and opening 2007 documents in 2003.
Hope this helps,