How to hide user account from Windows 7 welcome screen, without changing registry manually?

If you do "control userpasswords2" or "netplwiz" and add the user to the group IIS_IUSRS it will not appear in the login screen. However, this is not very useful as it simply disappears from the Welcome screen with no way to log in to it.

To set the Welcome screen to require input of a username as well as a password, do "secpol.msc", go to Local Policies > Security Options, and set "Interactive logon: Do not display last user name" to "Enabled".

It may also be that you unchecked the "Users must enter a username and password to use this computer" option in userpasswords2, so that the Welcome screen is bypassed entirely.