In Windows NT 4.0, when you had more items on the start menu than would fit in a column, multiple columns would be used.

In Windows 2000, the default is to scroll the start menu.

You can alter this behavior using Start / Settings / Taskbar & Start menu ... / Advanced. Uncheck Scroll the programs menu and press OK.

You can also alter the registry at:

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced

Edit StartMenuScrollPrograms, a type REG_SZ, and set the string to NO. You will need to restart your computer.