The security firewall program is usually the culprit when it comes to DSM installation problems. Defective hard drives, disk partition, and network connection issues can also be to blame. To resolve this, try doing the following: • Do an extensive disk scan on every hard drive you have on your Windows PC. The manufacturer has put a diagnostic tool in place, so use it so you can see if the disks are healthy. • After the scan finishes, format the disks on your Windows PC and then put them back on the Synology NAS. • The Synology NAS should then be connected to the PC with an Ethernet cable. Don’t go through a router to do this. • Use Synology Assistant to install DSM on the Synology NAS. If you use Kaspersky or ZoneAlarm, they have been known to block the connection between Synology NAS and Synology Assistant. It doesn’t matter if your firewall service is disabled, it can happen. The best way to get around this is to make sure your security software is totally disabled before doing DSM installation or when running Synology Assistant.