U guys are getting it all wrong
when office 2003 installs, it caches all the file it is using in a folder namde "MSOCache", for future use,
when U apply a service pack, all the files are first extracted in a folder names $Patchcache$ which is found in the folder C:\Windows\installer, this folder is a hidden system folder
now, if U are installing a new service pack, & it finds some files that it is supposed to update but it needs the source file which is not in the "MSOCache" thne it will ask for the CD or whatever source it was