Thank you for the update Tairni and we apologize for the delay in our response.

Unfortunately, this error is a bit vague so there are a few things you may want to try.

First try a clean boot. Simply open the task manager and select the 'Start up' tab. Disable everything here and restart the PC. This will make sure that no background processes are interfering with the game. make sure not to run any other programs when you play the game. This includes any overlays (Discord overlay, Geforce Experience, etc.), make sure these are disabled.

Try setting the compatibility mode to Windows 7. Right-click on the ffxivboot.exe file and select ‘Properties.’ Then select the ‘Compatibility’ tab and choose Windows 7.

When you reinstalled Windows, did you make sure to update it completely? You may want to check if there are any 'Optional' or 'Recommended' updates available that aren't installed automatically.

We hope we can be of assistance in helping you enjoy the exciting world of Final Fantasy XIV!