http://support.microsoft.com/default.aspx?scid=kb;en-us;822798
You Cannot Install Some Updates or Programs "Digital Signature not found"
When you use the Windows Update Web site to install updates, the installation fails
and the Windows Update.log file contains error 80070643.
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments. After that, you can post your question and our members will help you out.