See http://support.microsoft.com/kb/838687 "You receive an error
message when you install an Office program or open an Office
program or document".

Jack and Jill wrote:

Upgraded from Office 2000 to 2003
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\Curr entVersion\setup\OptionalComponents\MAPI.
Verify that you have sufficient permissions to access the registry or
contact your Information Technology department for assistance.

Office Installer starts running when first opening excel and then asks for
the Office 2003 standard disk, when you put the disk in then the above
message appears.