Cannot install Windows Server 2008 Service Pack 2 (SP2)

Applies to:

Windows Server 2008 Service Pack 2 (SP2)

Symptoms:

• Using Windows Update you get the error:
  
  0x800B0100
  TRUST_E_NOSIGNATURE
  No signature was present in the subject.
  
• Using the stand-alone installer for SP2 you get the error:
  
  "You need to install Windows Server Service Pack 1 before continuing"
  
• Or you cannot see/modify roles and features anymore.

How I solved it:

1. Run this tool (KB 947821).
   
2. Check %SYSTEMROOT%\Logs\CBS\CheckSUR.log for reported missing items (starting with "missing:") to find out which updates are blocking.
   
   In my case the resulting log included the following lines:
   

   Checking packages.
   (f) CBS MUM Missing 0x00000002 servicing\packages\Package_for_KB961371_server_0~31bf3856ad364e35~amd64~~6.0.1.4.mum  
   (f) CBS MUM Missing 0x00000002 servicing\packages\Package_for_KB961371_server~31bf3856ad364e35~amd64~~6.0.1.4.mum  
   (f) CBS MUM Missing 0x00000002 servicing\packages\Package_for_KB961371~31bf3856ad364e35~amd64~~6.0.1.4.mum 

   Checking component store
   Summary:
   Seconds executed: 270
   Found 3 errors
     CBS MUM Missing Total Count: 3
   

3. Either find the missing files on another machine OR download those updates from Microsoft and extract the .mum and .cat files from the update package (in my case: KB961371)
   (you can rename a .msu file to .cab and extract its contents.)
   (one of the .mum/.cat files should be missing in the package that you are looking for. Use update.mum and update.cat and rename them)
   
4. Copy the .mum and .cat files to C:\Windows\servicing\packages.
   (To be able to do so you need to take ownership of the folder and grant your user account full control. After copying the files set the owner back to "NT Service\TrustedInstaller")
   
5. Run the stand-alone installer for SP2.

Good luck & enjoy SP2!

(Thanks to Glafkos Charalambous as well as to the many people writing and answering on this topic on the TechNet forums)