How do you clear Mac install program files? I installed a 30-day "test drive" of QuarkXpress, but got pulled in to other projects and didn't have time to test it. I now need to test it, but the 30 days are up. So I want to install the "test drive" again, but it won't let me. So far, I uninstalled the old copy, signed up under a different account, and downloaded a new version. I know there has to be application data somewhere, but I am a PC person and don't know where to look in the Mac OS. HELP! Thanks.

Oh, and if necessary, I am using Mac OS X (Snow Leopard) Version 10.6.8 on a Mac Pro.
In the old days, changing the date, deleting the preferences, or installing the trial software in a different path did the trick, but, nowadays, it seems rather unlikely that there's such an easy way. 

Trial software may call home to check the database for a combination of your MAC address and your email, your IP, both, create an invisible file with a who-knows-which-name or a million different things. I mean, if there was an easy way to do so, you wont need the full version, right?

Someone might find a way, of course. But it will probably be for a specific program, not a generic way for all trial software.

EDIT: Just noticed that I'm not answering your question. Indeed, installed and used applications will leave other files, such as Preferences, stored either in your user's preferences folder (~/Library/Preferences) or in the System-Wide preferences folder  (/Library/Preferences/), or Application Support Files (which will be, again, in your user's library folder or in the root one). There could be a lot more, of course.

If you want to get rid of them, making a search, with Spotlight or Finder, should show them all.