Persistent "evaluation period has run out" message from a trial copy of a tool, while eval period still active

I've installed a trial version of a commercial tool on my machine running XP Pro. I am supposed to activate the trial period of one of its components by running a special command that they provide, that includes some sort of trial activation key. They supplied me with several alternative ones, but every time I try to activate, I get the message "Sorry, the evaluation period has run out." When I asked them whether it's possible to run any type of diagnostics tool they said that "they cannot reveal the workings of the trial version's protection system". This is understandable, but I can't run their tool on my machine. By the way, the activation works fine if I install it on another PC with XP Home. However, I need it to run on the XP Pro machine too. Is there any type of diagnostics tool that can be used to figure out what's going on. This is the first tool with which I've had this problem. However, if something is out of whack on my machine, is it possible to somehow detect it?