Thank you for your post.
For that message to appear, FileMaker Pro trial was installed earlier on that machine and launched. Unfortunately, there is no way to reset the 30-day trial on that machine. You will have to install the trial version on another machine.
Really? What a strange way to try and persuade people to buy your software! Oh well - guess I'll just have to wait for v11 and see if that works any better....
Now I'm no admin, but letting people repeatedly redownload a trial isn't really a good way to get people to "buy" your software either.
Something to think about...
Try to reformat your harddrive and install it again, it will surely work. :)