Just now, I uninstalled my VAIO Care on my PC because it can't work properly. So, how can I get it back again? Thank you.
It doesn't matter if you uninstalled the application or not, because it's always available for downloading from the Sony Support page. They offer all the original applications plus their updates, drivers and their updates, manuals, etc.
Access the following link, then expand the Vaio Care category. In that category, simply scroll down and locate the original package. Download and install it and then apply the available updates. Since the updates are provided in a combo package, it's not necessary to apply all the updates, only the latest one is recommended.