I just received a batch of five Dell laptops with Vista Home for a lab. One of the requirements was to have low privilege "Student" logins and the usual Administrator account for the instructors.
If you've dug around in Vista for any amount of time, you probably know by now the Administrator account is disabled by default to aid with keeping the system secure. Far too many Windows 2000/XP systems were left with blank administrator passwords and this is Microsoft's answer to that typical security hole.
Enabling the account readily accomplished in Vista Business, Enterprise or Ultimate. Go to Run... type lusrmgr.msc, click OK, highlight the Users folder, right-click Administrator in the right-hand pane, choose Propertiesand uncheck Account is disabled.
For the Vista Home Editions you have to do this via the command line (there is no Users Manager). Go to Start > Accessories and right-click Command Prompt and choose Run as administrator (this will prompt a UAC box, click Continue).
At the command prompt type: net user administrator /active:yes then hit enter.
Now the Administrator account will be available in the Control Panel > User Accounts applet. Lastly, but far from least: give this account a good password!