I tried copy/paste the file to another partition, would not work. tried it on another drive in the same computer, no can do, too. I had to make a new download. no problem because I just downloaded while I was sleeping.
just maybe you can copy/paste the downloader exe. never tried this. if you could do this, you would be able to save some time.
When the going gets tough, they call on the sons of ******s.
They only way I could see this working is if you copy the registry entries over with the maplestory/nexon folder (that is if maple is still adding registry entries, not sure if maple does this/still does this).
However you might be able to get away with it if you move the files over and then install NGM (Nexon game manager) so you can start maple from the site. If that doesn't work then you can always give him your installer (if you still have it) or just download it for him.
Link to NGM: http://nxcache.nexon.net/maplestory/ngm/maplestory-ngm-download.html