You can consider two options if you still want to use WinZip: either you completely uninstall it from your system and reinstall the trial version, or you can pay for it. An usual uninstall process using the Add/Remove Programs feature in Windows will leave traces of WinZip in the Windows registry and therefore if you reinstall the program it will show that the trial has expired. To avoid this you can use a more aggressive uninstaller like Revo Uninstaller who will search for remaining leftovers, or manually search the registry for WinZip entries and delete them. However, after you reinstall it, the trial will expire again someday. If you consider paying for the full version, you can purchase the software from the official WinZip website.