Hi Khalil,

Usually, if you have just installed Office without making a custom
installation, you won't be able to use the Excel 2003 application anymore.
That has been replaced by Excel 2007. Generally, what people do, if they
want to be able to use both applications is use the following KB article to
have both versions of Office installed:

http://support.microsoft.com/kb/290576/en-us
http://support.microsoft.com/kb/218861/en-us

I don't see an updated one for Office 2007 but would assume that it's the
same sort of process. Install the Office package to different folder
locations, i.e. C:\Program Files\Microsoft Office\Office 2003 and C:\Program
Files\Microsoft Office\Office 2007.

Bare in mind that when switching applications you should have two separate
links to the different applications, open link to Excel 2003, close then
Open link to Excel 2007. Also, first time you launch Excel version after you
have launched the previous version, it will may to re-initialise first time
routines (because previous version settings are in place). Also, you won't
be able to run them concurrently. If you open the 2003 version, every
instance you open (when there is an instance still running, will be 2003).

Hope that helps.