TweakUI is a popular system configuration utility made by Microsoft since late Windows 95, and it provides quick and easy access to configure certain features in Windows without resorting to registry editing or other more dangerous tactics. Its not the best software ever created, but its a nifty tool to have. You can download it at the Microsoft downloads page or at filehippo.
To get TweakUI working on Windows Vista, just download the XP version with the correct architecture (i.e. if you have Vista x64 download TweakUI x64, and if you have Vista x86 download the x86 edition). After setup is finished, right click the shortcut to TweakUI -> Properties -> Compatibility. Set it to run as an administrator and in XP compatibility mode. Close the dialog box and run the application.
To hide User's accounts on Welcome screen, 1) Run the software 2) In the tree pane on the left, navigate to and select Login 3) In the right pane, UNTICK the account(s) you want to hide. There are many settings you can configure with this simple tool. Just feel free to explore.