How to manually start windows update

From command line, force detect with:

wuauclt /detectnow

To troubleshoot machines updating from my WSUS server.

I am not sure if it will apply to normal online updating but it is worth mentioning.

Troubleshoot update issues with this logfile:

%windir%\windowsupdate.log   

If you are using Windows 10, Windows updates are logged with ETW (Event Tracing for Windows): https://support.microsoft.com/en-us/kb/3036646

Another way to manually begin the windows update procedure in XP is to restart it from the Control Panel:

• Control Panel -> System
• Go to 'Automatic Updates' tab
• Temporarily turn off updates: check 'Turn off Automatic Updates.' -> Apply
• Turn them back on: check 'Automatic' tab (or whichever option you normally use) -> Apply

This forces Automatic Updates to restart, and the result can be seen in the logfile

%windir%\WindowsUpdate.log

This is also a great way to restart AU downloads if they have been interrupted for some reason.