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