You can start Recovery Console and from a command prompt change to the
%SystemRoot%$NtServicePackuninstall$\spuninst
directory. Then issue the command
batch SPuninst.bat
The next step is to start in 'Safe Mode' and uninstall the SP again from
Control Panel|Add/Remove to finish the uninstall.
To start the Recovery Console, start the computer from the Windows 2000
Setup CD or the Windows 2000 Setup floppy disks. If you do not have Setup
floppy disks and your computer cannot start from the Windows 2000 Setup CD,
use another Windows 2000-based computer to create the Setup floppy disks.
Press ENTER at the "Setup Notification" screen. Press R to repair a Windows
2000 installation, and then press C to use the Recovery Console. The
Recovery Console then prompts you for the administrator password. If you do
not have the correct password, Recovery Console does not allow access to the
computer. If an incorrect password is entered three times, the Recovery
Console quits and restarts the computer. Once the password has been
validated, you have full access to the Recovery Console, but limited access
to the hard disk. You can only access the following folders on your
computer: %systemroot% and %windir%