If you installed Multiprocessor support after installing Windows NT, using Uptomp from the Resource Kit, the Compaq SSD, or similar means to upgrade to MPS, the %SystemRoot%\Repair\Setup.log did not get updated. When you applied the Service Pack, it copied the Uniprocessor Hal.dll that was originally installed when you first setup Windows NT.
To correct the problem for Windows NT 4.0, modify the %SystemRoot%\Repair\Setup.log file and re-apply the Service Pack:
1) attrib -r -h %SystemRoot%\Repair\Setup.log
2) Make a backup copy of the %SystemRoot%\Repair\Setup.log.
3) Edit Setup.log, search for these five lines, changing the string after the = sign:
\\System32\Ntoskrnl.exe = "NTKRNLMP.EXE","d89e8"
\\System32\Kernel32.dll = "KERNEL32.DLL","5b7f8"
\\System32\Ntdll.dll = "NTDLL.DLL","59c19"
\\System32\win32k.sys = "WIN32K.SYS","132603"
4) Select ONE of the following HAL's and modify the line:
\\System32\hal.dll = "HALSP.DLL","0f337"
\\System32\hal.dll = "HALMPS.DLL","1a01c"
HALSP.DLL is or Compaq Systempro,Systempro/XL, ProLiant 2000, 4000, and 4500 systems only
HALMPS.DLL = Multiprocessor HAL for APIC support and for the Compaq ProLiant 1500 and 5000
5) Save the modified Setup.log to the %SystemRoot%\Repair directory and attrib +r +h %SystemRoot%\Repair\Setup.log
6) Re-apply the service pack.