The Sygate Uninstall utility is part of the program when it is installed,
however, sometimes, the program is removed, but NOT the folder.
So....go into the My Computer, Programs and look for Sygate folder. If its there, open up each folder and sub folder and look for a file called Uninstall. Clicking on this should run the uninstall utility again.
If this fails to solve the problem, then you more than likely will need to do this: (even though it sounds silly):
Uninstall Zone Alarm and reboot.
Attempt to install Sygate again but this time shut down all non essential programs except Systray and Explorer using the Shutdown Dialog menu (Hold Ctl. Alt and then the Delete key)
If Sygate installs, then you can try it, if not, THEN go into the Programs/Sygate folder and find Uninstall. Click it again and everything should come out. REBOOT.
Then go put Zone Alarm back in.
I know this sounds tedious, but something was not removed and Zone Alarm sees it, or
thinks it sees it!
Either way, you need to go back to square one and start over.