If your Secundary Logon service has gone missing it can be reinstalled with the following:
1. Make sure the files runas.exe and seclogon.dll is present in the c:\windows\system32\ folder
keep in mind that seclogon.dll is a system file that might be hidden, so search for the file rather than browse.
if the files are not in the folder, they can be copied from the attached .zip file.
2. set the following registry keys:
Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\seclogon]
"DisplayName"="@%SystemRoot%\\system32\\seclogon.dll,-7001"
"ImagePath"=hex(2):25,00,77,00,69,00,6e,00,64,00,69,00,72,00,25,00,5c,00,73,00,\
79,00,73,00,74,00,65,00,6d,00,33,00,32,00,5c,00,73,00,76,00,63,00,68,00,6f,\
00,73,00,74,00,2e,00,65,00,78,00,65,00,20,00,2d,00,6b,00,20,00,6e,00,65,00,\
74,00,73,00,76,00,63,00,73,00,00,00
"Description"="@%SystemRoot%\\system32\\seclogon.dll,-7000"
"ObjectName"="LocalSystem"
"ErrorControl"=dword:00000001
"Start"=dword:00000003
"Type"=dword:00000020
"RequiredPrivileges"=hex(7):53,00,65,00,54,00,63,00,62,00,50,00,72,00,69,00,76,\
00,69,00,6c,00,65,00,67,00,65,00,00,00,53,00,65,00,52,00,65,00,73,00,74,00,\
6f,00,72,00,65,00,50,00,72,00,69,00,76,00,69,00,6c,00,65,00,67,00,65,00,00,\
00,53,00,65,00,42,00,61,00,63,00,6b,00,75,00,70,00,50,00,72,00,69,00,76,00,\
69,00,6c,00,65,00,67,00,65,00,00,00,53,00,65,00,41,00,73,00,73,00,69,00,67,\
00,6e,00,50,00,72,00,69,00,6d,00,61,00,72,00,79,00,54,00,6f,00,6b,00,65,00,\
6e,00,50,00,72,00,69,00,76,00,69,00,6c,00,65,00,67,00,65,00,00,00,53,00,65,\
00,49,00,6e,00,63,00,72,00,65,00,61,00,73,00,65,00,51,00,75,00,6f,00,74,00,\
61,00,50,00,72,00,69,00,76,00,69,00,6c,00,65,00,67,00,65,00,00,00,53,00,65,\
00,49,00,6d,00,70,00,65,00,72,00,73,00,6f,00,6e,00,61,00,74,00,65,00,50,00,\
72,00,69,00,76,00,69,00,6c,00,65,00,67,00,65,00,00,00,00,00
"FailureActions"=hex:80,51,01,00,00,00,00,00,00,00,00,00,03,00,00,00,14,00,00,\
00,01,00,00,00,c0,d4,01,00,01,00,00,00,e0,93,04,00,00,00,00,00,00,00,00,00
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\seclogon\Parameters]
"ServiceDll"=hex(2):25,00,77,00,69,00,6e,00,64,00,69,00,72,00,25,00,5c,00,73,\
00,79,00,73,00,74,00,65,00,6d,00,33,00,32,00,5c,00,73,00,65,00,63,00,6c,00,\
6f,00,67,00,6f,00,6e,00,2e,00,64,00,6c,00,6c,00,00,00
"ServiceMain"="SvcEntry_Seclogon"
"ServiceDllUnloadOnStop"=dword:00000001
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\seclogon\Security]
"Security"=hex:01,00,14,80,a0,00,00,00,ac,00,00,00,14,00,00,00,30,00,00,00,02,\
00,1c,00,01,00,00,00,02,80,14,00,ff,01,0f,00,01,01,00,00,00,00,00,01,00,00,\
00,00,02,00,70,00,05,00,00,00,00,00,14,00,fd,01,02,00,01,01,00,00,00,00,00,\
05,12,00,00,00,00,00,18,00,ff,01,0f,00,01,02,00,00,00,00,00,05,20,00,00,00,\
20,02,00,00,00,00,14,00,dd,01,02,00,01,01,00,00,00,00,00,05,04,00,00,00,00,\
00,14,00,cd,01,02,00,01,01,00,00,00,00,00,05,06,00,00,00,00,00,14,00,dd,01,\
02,00,01,01,00,00,00,00,00,05,0b,00,00,00,01,01,00,00,00,00,00,05,12,00,00,\
00,01,01,00,00,00,00,00,05,12,00,00,00
3. Reboot your computer
I have attached a .zip files with a msi installer that sets the above settings for you, also included in the file is the runas.exe and seclogon.dll