On Windows XP, if you launch the installer and the Wise Installer screen flashes briefly instead of starting the install sequence, hit Control+Alt+Delete to bring up the Task Manager. Click the Processes tab and check to see if you have a process called support.exe running. If you do, select it and click End Process. Final Draft should then install without a problem.
NOTE: Live support for Final Draft 7 has been discontinued. You will still be able to install, activate and use FD7 on appropriate computers but email, chat and telephone support is no longer available. Live activation assistance is still available via phone (818-789-6281) and email and chat (links on the left side of this page).