The Windows 7 Welcome screen is a security feature to prevent unauthorized access to your computer. For some people, however, convenience is more important than security. If you're not concerned about security and prefer to have your computer boot straight into the Windows desktop, here's how:
Step 1: Search for netplwiz in the Windows search box and hit the Enter key.
Step 2: Uncheck the box next to "Users must enter a username and password to use this computer" and click OK.
Step 3: Enter the username you'd like to automatically log on and the password for that account, then click OK.
That's it. Now your Windows 7 computer will boot into the Windows desktop automatically. Aside from being convenient, this is a good way to record boot times, if you're into that sort of thing.
Just remember, once you do this, anyone who comes across your computer can access your files, make changes to your system, or install malware with ease. Be warned!