I have and use EQ5 as well. Since I probably don't use it to it's full potential, I've not seen the need to upgrade. When I initially re-installed it on my new computer I got some kind of message saying something or other wouldn't work correctly or at all - don't really remember as it's been a few years. But other than the shortcut Icon on my desktop looking funky at first, I haven't had any issues. Am able to open existing or begin new projects; don't seem to have any command issues at all. And now the Icon looks normal. Sorry, can't help offhand with what OS I'm using on the computer it's installed on. Using DH's laptop now and the EQ is on the upstairs desktop.