This error 0x80072F76 means: "ERROR HTTP HEADER NOF FOUND". That is the HTTP header cannot be found.
Suggestion one:
It you have installed an Internet accelerator (web accelerator) such as NetZero HiSpeed, or similar, disable it and go to Windows Update.
Suggestion two:
If the first suggestion has not solved the issue, or you have not got any web accelerator, try this: Start > Run and type in this lines, and hit ENTER key after each one:
