He does not need a disk image if he has the Full Offline Installer for the older version he wants. That said, while there have been some glitches reported on 17.6.2310 most people have not had issues. My 2 computers are running it and so far, they are fine. One is a XP PRO SP3 P4 box and the other a Toshiba Laptop with Windows 10 Home 64 Bi t