That's a Postgres database, and for that type of database if you deleted any of the files you'd have to restore the database from a backup or repair the database so that it could work again. Unfortunately for databases you can't really safely delete anything with Windows Explorer.
Not sure if there was a typo but that database might not be part of EventSentry? Your EventSentry database would be the entire "C:\Program Files (x86)\EventSentry\data" folder or the entire "C:\Program Files (x86)\EventSentry\data96" folder. Just being in "C:\Program Files (x86)" isn't necessarily an EventSentry database.
If your database actually is in an EventSentry folder and is part of EventSentry, you might want to see if there is any old data that you want to remove. That will free up space inside the database so that the database stops growing and eating up more of your hard drive. You can use this article to remove old data: https://www.eventsentry.com/kb/183
Once you have some free space inside the database, you can use this article to get some disk space freed up: https://www.eventsentry.com/kb/241
If you have a support/maintenance contract with EventSentry you can also submit a ticket to them about shrinking your Postgres database and they can have you run some scripts that will get back a bunch of your free space without needing 1.5x the database size already available as free disk space and without you having to backup/drop/restore the whole database either.