H2SO4...would you recommend using the built in account?
Bit of background first...
NT was the first Windows flavour to earn a "C2" security rating. Short version: "this is a sufficiently secure OS for government use, as long as you post an armed guard outside the room and disallow physical access to unauthorised staff."
The implication of physical access is that any software-based security can be circumvented. You've locked down your machine and the admin account has a 64-char random passphrase? No big deal. Somebody with physical access can still boot into another OS and rummage round. This principle is demonstrated all the time by Xbox modders and the like - somebody with physical access has defeated even the most carefully thought-out security scheme, and one which was partially implemented in hardware for that matter.
Differences between in-built and other "admin" accounts:
There are no significant differences, except for the aforementioned deletion protection for the in-built account. Anybody with admin privileges can inspect, modify, disrupt, or destroy the workings of any app or the OS itself, plus they can free themselves from any attempts to hobble their particular account. This is frequently misunderstood by management in large organisations whose "domain admins" groups have over time accumulated 376 separate accounts. They panic because they realise that far too many people have unrestricted access to the company's systems and data, and they seek ways to "limit some of the administrators". That of course fails, because admins cannot be limited, and then they're left with needing to reorganise their security design. Telling Joe from Marketing that he no longer has admin rights is always a political bunfight.
Re "using the in-built admin account":
As with all admin accounts, they should only be used for those system administration tasks which require admin privileges, as I believe you and others have already said on this thread. For daily tasks, a low-privilege (non-admin) account is perfectly sufficient, and it is much safer. Always logging on using (any) admin account, reading email, browsing the web, downloading shareware, and doing everything else as an admin is just askin' for it
EDIT: Oh, one more thing. The in-built admin account is not entirely disabled by default. On non-domain-joined machines, which would include most of ours here, if there are no other admin accounts the in-built one can be used to log on in safe mode, irrespective of whether it has first been "enabled" or not. Again, it's done so that there's no possibility of finding yourself with only one admin account - which happens to be locked out because it was never "enabled"
