
Hello djsorg2062,
Hauptwerk v4 is no longer available for download (or supported in any way), I'm afraid.
If you bought an entirely new full licence for v5+, as opposed to upgrading your v4 licence to v5+, and if you still have the installer for v4, then you could potentially install v4 on a separate computer and use it simultaneously with v5+ (running on another computer). However, if you upgraded your v4 licence to v5+ then you can't keep using v4, I'm afraid. (Also, migrating your sample set licences from v4 to v5+ would have wiped your v4 licence from the Hauptwerk v4 USB Key.)
(With just a single v5+ licence) you can, however, install v5+ on as many computers as you wish, provided that only one of them is actually running Hauptwerk at any given moment (with your v5+ iLok dongle attached to that computer). I.e. you can freely move your iLok dongle between several computers, provided that you exit Hauptwerk before doing so.