Control Panel > User Accounts > "Change the way users log on or off" > Uncheck both "Use the Welcome screen" and "Use Fast User Switching"
For more security, in which when the log on windows appears, this will make it so it doesn't display the user that logged on last:
Control Panel > Administrative Tools > Local Security Policy
Expand the Local Policies branch, and double-click the Security Options. Look for "Interactive Logon: Do not display last user name", and enable it.
There's a plethora of things to be tweak. Just be curious, and look around. Just be sure to write it down or something for future reference.
Happy New Year!
Bryan