Not sure where else to post, but is there a fix?

Your Project Diablo 2 was flagged in windows antivirus, just whitelist it and push back the pd2.dll that it removed.

So do I need to reinstall and do it all over again? Or simply turn it off

You should be able to do exactly what I said above in your windows antivirus. It'll be logged, all you do is push back the file it took and whitelist it.