And the uninstaller that VTMac speaks of can be found on the disc image with all of the more recent versions (beta and GA) of the Parallels installer.
If I remember correctly, it asks you to restart after uninstalling; this is because the uninstaller erases the kernel extension from your hard disk, but it is still running in your system until you restart.
[\begin rant]
Also, I just thought I would point something out, because there have been so much discussion lately on other threads (NOT this thread) regarding User's Requests/Demands vs. Parallels Responsiveness. A few months back (before GA release) there was LOTS of complaining about Parallels installing kernel extensions and not providing an accompanying uninstaller. Then there was further complaining about Parallels not responding to these initial complaints. Well, in hindsight, it looks like they weren't responding because they were busy building an uninstaller and actually addressing the problem in their software rather than addressing their user forum. My point is, some people are so quick to judge Parallels based on their forum presence rather than their product performance, but Parallels proves again and again that one must be patient and they will eventually come through. I'm sure this will prove to be the case with USB2, Graphics accelleration, etc., all of which they have promised they are working on. Personally, I am glad that they are actually working on it rather than spending all their time replying to the forum.
[\end rant]