My previous post described how to add information to and otherwise customize Windows' Welcome screen. But maybe you just want to get your PC going without having to log into an account. You can bypass Windows' log-on screen by changing settings in the Windows Registry, as described in a tutorial on the Computer Performance site, but I find it much simpler to use a free Windows-tweaking utility to do the same thing.
The program I used to customize the Windows Welcome screen—TweakNow PowerPack 2009—is the same tool I used to disable the log-on screen on my Vista laptop. Click Windows Secret in the utility's left pane and choose User Accounts. Click "Enable auto log-on," select the account you want to log into automatically, enter the account's password and domain name (if necessary), and click Save. The next time you start the PC, Windows will start and open that account automatically.
TweakNow PowerPack 2009 works with XP, Vista, and Windows 7, but I tested it only with Vista. I didn't need to download the program to my XP test machine because that system already has Tweak UI, Microsoft's free XP-reconfiguration utility that lacks a Vista version.
To set XP to start a specific account without requiring a log-on, open Tweak UI and click Logon > Autologon in the left pane, check "Log on automatically at system startup" in the right window, enter the account's user name and domain (if necessary), and click the Set Password button.
In the Set Autologon Password dialog box, enter the account's password in each of the two text boxes and click OK.
Why bypassing the Windows log-on is dangerous
Setting Windows to open an administrator account automatically is risky, period. Even starting a standard account without requiring a password is dangerous, though less so. There are many very good reasons why Windows accounts are password-protected, and far fewer good reasons for doing without passwords.
That's why I recommend against allowing automatic log-ons in general. But far be it from me to tell you how to use your PC, so if you want to save a few seconds each time you start your system—and you're not worried about somebody doing serious mischief after gaining easy access to your account—it's okay by me.