Start-up menu change to leave login blank

There are a couple of ways to do this: a utility and a direct hack to the Registry. The utility is TweakUI, which...

is available on the Windows 2000 Resource Kit. This tool contains a multitabbed interface that controls lots of little interface parameters, including the last logon display.

The direct hack method goes like this. Open Regedit and drill down through Hkey_Local_Machine | Software | Microsoft | Windows NT | CurrentVersion | Winlogon. This is the key that controls the Graphical Identification and Authentication (GINA) window. Find the DontDisplayLastUserName entry and change the value from 0 to 1.

In your situation, the Registry hack is probably going to be the simplest to deploy to users. Save the entry using Regedit via Files | Export Registry File. Give it a name like NoName.Reg. Then edit the file and remove all but the entry you're going to distribute. It will look something like this:

Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsNTCurrentVersionWinlogon]
"DontDisplayLastUserName"="1"

Then put a line in your logon script like this.
Regedit /s noname.reg