So we had to get a new iMac for a copywriter and he uses it as a basic screener to view the Avid projects we're working on. These copywriters have their own bins and projects separate from the editors so they don't mess up editors projects, and they have read-only access to all media.

Since I can't downgrade the iMac, which came preloaded with 10.5.2, is it even possible to load Express 5.7.3? Will it even run or will their be crashes galore?

Just thought I'd get some input before I tell him he can no longer watch stuff on his iMac...

Sure it's possible. You can't use a mojo or anything but a few folks have run it on Leopard here.

I just tried loading it and got an error while installing. Something about an error writing the postflight to the extensions... So I uninstalled everything. Actually the unistaller wouldn't work so I had to manually delete everything... but it's all uninstalled now...

That and my dongle wouldn't work when I tried to open Xpress Pro. Got the error that it couldn't locate a dongle...