Run regedit
In [HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\WindowsUpdate\AU]
Edit > New > DWORD:
"RebootRelaunchTimeoutEnabled" with a value of "1"
Edit > New > DWORD:
"RebootRelaunchTimeout" with a value of the time in minutes until the next prompt. "1440" (24 hours) looks like the max. If you input "0" for this DWORD or the former, it will default to 10.
source:
http://lifehacker.com/software/top/get-rid-of-win...art-nag-183976.php