Most of the "free trial" stuff I've run into puts a "timestamp" on the machine when you install it, so that they know when to bug you about paying for it; but if you uninstall, the "timestamp" is also removed, since it's usually in an install log that goes away with the program. You can usually re-install and start fresh without much hassle. (I've reinstalled the demo Sibelius about 4 times - and still can't convince myself I should cough up the extortion fee to buy it.)

The problem with reinstalling AV or Firewall stuff from an "old" version is that the "signature" files will be out of date so rapidly that you probably should see if you can download a "fresh" copy (if you got it via download), just so it's got what's going on now (or at least recently) instead of "protecting you" from stuff that's so old it doesn't circulate much any more.

John