Comprehensive logging in Windows Update in Windows 7

If you want to turn on verbose logging for Windows Update and the Microsoft Installer, then you could follow KB 2545723 - How to Enable Microsoft Installer logging and Verbose logging to gather additional troubleshooting Information... or if you are masochistic enough then you can copy the following into a .reg file, then open this to import it into your registry:

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Trace]
"Level"=dword:00000004
"Flags"=dword:00000007

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Trace\Agent]
"Flags"=dword:000000ff
"Level"=dword:00000004

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Trace\ARP]
"Flags"=dword:000000ff
"Level"=dword:00000004

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Trace\AU]
"Flags"=dword:000000ff
"Level"=dword:00000004

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Trace\AUClnt]
"Flags"=dword:000000ff
"Level"=dword:00000004

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Trace\CDM]
"Flags"=dword:000000ff
"Level"=dword:00000004

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Trace\CltUI]
"Flags"=dword:000000ff
"Level"=dword:00000004

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Trace\Cmpress]
"Flags"=dword:000000ff
"Level"=dword:00000004

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Trace\COMAPI]
"Flags"=dword:000000ff
"Level"=dword:00000004

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Trace\CPL]
"Flags"=dword:000000ff
"Level"=dword:00000004

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Trace\DnldMgr]
"Flags"=dword:000000ff
"Level"=dword:00000004

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Trace\Driver]
"Flags"=dword:000000ff
"Level"=dword:00000004

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Trace\DtaStor]
"Flags"=dword:000000ff
"Level"=dword:00000004

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Trace\EEHndlr]
"Flags"=dword:000000ff
"Level"=dword:00000004

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Trace\Handler]
"Flags"=dword:000000ff
"Level"=dword:00000004

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Trace\Inv]
"Flags"=dword:000000ff
"Level"=dword:00000004

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Trace\Misc]
"Flags"=dword:000000ff
"Level"=dword:00000004

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Trace\OfflSnc]
"Flags"=dword:000000ff
"Level"=dword:00000004

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Trace\Parser]
"Level"=dword:00000004
"Flags"=dword:000000ff

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Trace\Perf,]
"Flags"=dword:000000ff
"Level"=dword:00000004

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Trace\PT]
"Flags"=dword:000000ff
"Level"=dword:00000004

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Trace\Report]
"Flags"=dword:000000ff
"Level"=dword:00000004

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Trace\Services]
"Flags"=dword:000000ff
"Level"=dword:00000004

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Trace\Setup]
"Flags"=dword:000000ff
"Level"=dword:00000004

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Trace\Shutdwn]
"Flags"=dword:000000ff
"Level"=dword:00000004

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Trace\Trace]
"Flags"=dword:000000ff
"Level"=dword:00000004

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Trace\TraceTestMain]
"Flags"=dword:000000ff
"Level"=dword:00000004

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Trace\TraceTestThreads]
"Flags"=dword:000000ff
"Level"=dword:00000004

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Trace\WUApp]
"Flags"=dword:000000ff
"Level"=dword:00000004

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Trace\WuRedir]
"Flags"=dword:000000ff
"Level"=dword:00000004

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Trace\WUWeb]
"Flags"=dword:000000ff
"Level"=dword:00000004

[HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\Installer]
"Logging"="voicewarmupx" 
"Debug"=dword:00000007

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Trace]
"Flags"=dword:00000016
"Level"=dword:00000004

Every 200MB or so, it truncates the file and starts again, so you will also need to open Powershell and run the following:

Get-Content -Path "C:\Windows\WindowsUpdate.log" -Wait > "C:\output\giganticlogfile.log"