I usual set the Admin password when loading the operating system (XP).
What shows at normal boot then is the user accouints - mostly limited accounts and perhaps one is also admin account. Lets say I'm setting up a desktop PC for a family to use - the children each has their own limited account with own password and the oldest child or a parent may also have an admin privs on their account because they are expected to be in charge of things for the benefit of others.
The admin account which was set at load up time is the Administrator's account and only shows up in Safe Mode, Recovery concole, etc...it is not the same admin account that a parent or older child has (although it can be) and doesn't show up at normal boot. You boot into Safe Mode and use Administrator when you need to troubleshoot the system.
If no password is set for Administrator when first loading up the system, then there will be no password for Admin in Safe Mode. When asked for a password, you just click through on the empty password box - that is, instead of entering anything in the box. Like Frank says - this is the default setting - and this can be a handy option to have --
The Safe Mode Administrator account is there so the clued-in can reset passwords if the clue-less forget them. It has no password by default.
