Remove your HDD(s) from the tray (if for TS-109, the same).
Boot up the NAS without HDD(s) installed. You will hear a short beep, and after about 1~2 minutes, a long beep.
The system will use the embedded image to boot up.
Then run the Finder on your PC, it will help you to find the NAS on the network.
Use the default ID (admin) and password (admin) to login if it asks.
Hot-plug the HDD(s) into the NAS.
Go through the installation process including formating hard disk and installing the firmware.
Method 2 (Manually removing partitions using a Windows PC)
Shut down the NAS and remove the HDD(s) from the tray.
Install the HDD(s) in a Microsoft Windows client machine.
Boot the client computer and open the Computer Management application. (Right click My Computer --> Manage)
Locate the HDD(s) from the NAS in the Disk Management section and delete all the partitions.
Shut down the client computer and remove the HDD(s).
Install the HDD(s) in the NAS.
Boot the NAS. As there is no OS installed the NAS uses its embedded image to boot.
Run the QNAP Finder application on the client machine to locate and connect to the NAS.
Use the default username (admin) and password (admin) to login if it ask.
Go through the installation process including formatting the HDD(s) and installing the firmware.