Side-by-side configuration is incorrect

Hi folks -

Just started getting these two errors that seem to be related:

"The application has filed to start because its side-by-side configuration is incorrect.  Please see the application event log for more detail." (when I try to run Word or Quicken or Adobe Acrobat Reader)

When I try to start Excel (C:\Program Files\Microsoft Office\Office 12\EXCEL.EXE) the error is "This file does not have a program associated with it for performing this action.  Create an association in the Set Associations control panel."

Any ideas?

Thanks.

My computer is Inspiron 1520 running Vista SP 1