I've found a lot of information on the subject on various blogs and forums, strangely everyone seems to come to the conclusion that it is impossible to get back to the old style logon screen that appeared like this under Windows XP:
Why would anyone do this?
Why would you go back to something like this? There could be thousands of reasons. The default logon screen of Windows 7 looks like this:
So how do you restore the good old logon screen with a simple text box for the user name, and a simple text box for the password? It's actually a lot simpler than some people would think.
Local security policy management console
Press Windows+R to get the "Run" dialog, and enter "secpol.msc" in the text box then click OK. You are opening up the Local security policy management console.
In the option tree on the left, go to "Security Settings" / "Local Policies" / "Security options".
In the list of settings on the right, locate "Interactive logon: Do not display last user name". Double click this setting and in the box that shows up, select "Enabled" and click OK. Restart your computer... and voila!
You can also change a couple of other settings, such as disabling the annoying "Ctrl+alt+del" screen, the option right below the one I just described.
Once you're all done you'll be seeing a screen like this when you start up your computer. If you didn't join a domain obviously you won't be seeing the domain part.