SBS 2008 is designed from the ground up as a secure environment. So much so that Microsoft designed it so that the Administrator account (often called the –500 account) is actually disabled during the setup of SBS 2008. Instead, during SBS 2008 setup, Microsoft ask you to give a name to create a brand new Network Administrator account. They do this so that each installation of SBS 2008 will be different and therefore make it harder to attack from a brute force password cracking attempt.
The question that I’ve heard from some however is when if ever should I use the inbuilt Administrator account in SBS 2008?
In reality – for all the installations I’ve done so far, I would have to say never. I’ve never been in a situation where I’ve needed to re-enable the inbuilt Administrator account. So in my mind… you should certainly NEVER enable it and leave it enabled. However if you do find you are having a very strange problem with installing software on your SBS 2008 server then it is certainly something I might try, but I would ensure that it was disabled again shortly there after.