Unable to open downloaded items in MS Office 2010

I’m using MS Office 2010, and I’m trying to open some downloaded items but I can’t open it in any formats at all. I tried to open the files that I’m able to open before with MS Office 2010 but I could not open it now. I only get error messages depending on the program I’m trying to open. Some error messages are: there is a problem with the contents, file may be in use by another application, or file may be corrupted. Can you please help me to fix this?
