How often Automatic Updates run?

Hello all
I red about the following registry keys
ScheduledInstallDay and ScheduledInstallTime
letting you decide when AU should INSTALL the downloaded (depending on
AUOptions setting).
But what about CHECKING for updates? How often it runs?

thanks
fefone

my registry keys...

[HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Win dows\WindowsUpdate]
"WUServer"="http://MyServer"
"WUStatusServer"="http://MyServer"

[HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Win dows\WindowsUpdate\AU]
"NoAutoUpdate"=dword:00000000
"UseWUServer"=dword:00000001
"AUOptions"=dword:00000002
"ScheduledInstallDay"=dword:00000000
"ScheduledInstallTime"=dword:0000000c
"RescheduleWaitTime"=dword:0000000f
"NoAutoRebootWithLoggedOnUsers"=dword:00000000