I have numerous Excel files from Microsoft Office 2003. I am using XP Media Center. All of a sudden, these files will not open from documents. They will open if you open a new Excel book and file>open from there. Also, they will open from documents if (and only if) there is a new Excel book open at that time in a separate window. In summary, I can open Excel files any way I want, but only if a fresh workbook is opened.

There is no virus or spyware so far as I know. The file names are still correct. I ran run>excel /regserver and this didn't change anything. I have not tried unreg yet for fear of making the situation worse. Ignore Other Applications is unchecked in Tools>Options>General.

Has anyone ever solved this thing before? I've already spent almost 1 1/2 hours on this and I have used up everything I know, so thanks for any advice.