If you see an error mentioning 'DDay.Update', such as the message below, please following the instructions below this message.

Install Error
There has been an unexpected error. Please try again.
Object reference not set to an instance of an object.
at DDay.Update.UpdateManager

Solution:

In order to correct this problem, you would need to uninstall the game as per normal from Control Panel, Programs and Features in Windows Vista/7 or Add/Remove programs in Windows XP.

Once the Stronghold Kingdoms has been removed you will need to manually delete some hidden files, so you may want to turn them on/visible (operating system dependant where it'll be located) :

Windows XP
C:\Documents and Settings\User\Application Data\Firefly Studios\Stronghold Kingdoms (hidden folders needs turning on)
C:\Program Files\Firefly Studios and delete the Stronghold Kingdoms folder.

Windows Vista 32/64 / Windows 7 32/64
C:\Users\[USERNAME]\AppData (hidden folder)\Roaming\Firefly Studios\Stronghold Kingdoms
C:\Program Files\Firefly Studios and delete the Stronghold Kingdoms folder.

Open the website, download and install Stronghold Kingdoms as normal.

Please also ensure that you have a stable internet connection and that you are not using a VPN or having your internet traffic monitored or restricted in any way.