If you've installed java in your Windows, the java will automatically run an auto update periodically. If you are using Vista or Windows 7, the annoying UAC will prompt you every time when the system try to run the auto updater. To disable this, edit the registry:

[HKEY_LOCAL_MACHINE\SOFTWARE\JavaSoft\Java Update\Policy]
"EnableAutoUpdateCheck"=dword:00000000

Ref: http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6294083