Windows 2000 service pack problem

I have a computer running Windows 2000 that I cannot install service pack 3 or 4 on. When I install the service pack it installs ok but the computer locks when shutting down. This forces you to power it off. When you start it back up it will give you a BSOD (KMODE_EXCEPTION_NOT_HANDLED… in NTOSKRNL.EXE.) Removing the SP from safe mode fixes the problem. This is preventing me from installing the Blaster patch and other hotfixes etc.