Much software today, especially MS, caches the location it was installed from, whether a cd, a mapped network drive or a UNC path. This can be a problem if you are trying to install software across many international sites with roaming users, as the software will usually attemnpt to contact its point of origin.
To get round this make the admin point or software share for the software a DFS mount point. Then replicate these DFS shares across the organisation. The software will then automatically be directed towards the nearest DFS mount, rather than its original.
You can even use this with SMS as you can create a package without source files and just run the command line from the DFS share.