The Launcher reads as a virus for some unknown reason to me.
I suggest clicking on the arrow on the bottom right screen, and "quit" the anti-virus for the moment.
Or click on the little shield, it should bring you to Windows Defender Security Center.
On the left, select Virus & Real Treat Protection, then on the right side select Virus & Threat Protections Settings.
In that setting, turn off the first three tabs that you see, then try to download the PSO Launcher. It should work then.
Don't forget to turn on those virus protection tabs later on.