It is not necessary, usually, to un-install WebAccess before installing a new version.
If you use un-install before installing an updated version of WebAccess, be sure to Reboot before running Setup.exe. This is because during uninstall, the program files that are in use cannot be erased; the uninstaller marks the programs to be deleted at the next reboot. If you install new versions of these programs after running uninstall and before a reboot, the uninstaller will erase the new versions of these programs.