Windows Update Service Missing

Fix: Download the Windows Update Agent and force it to install.

Step 1. Download the Windows Update Agent:
WindowsUpdateAgent30-x86.exe
WindowsUpdateAgent30-x64.exe

Microsoft KB 949104


Step 2. Force the installation
If installing the agent fails because it is already installed, you can force the install:

WindowsUpdateAgnet30-(x86/x64).exe /wuforce


Finally, you probably want to run a spyware scan (eg. Spybot Search & Destroy or Malwarebytes) because chances are pretty good you've got something. I routinely disable System Restore in these scenarios because that garbage likes to hide in there.