Configure non-domain Windows 2000 client for AU

Replace Windows\Inf\wuau.adm with the one from XP SP2

Open gpedit.msc
Expand Computer Configuration node
Right click on Administrative Template
Click Add/remove templates
Add wuau.adm
Configure Windows Update options

Run wuauclt /detectnow

Inspect WindowsUpdate.log
If there is any error, try the following step

Replace several EXE and DLL on Windows\System32 with the ones from XP SP2
(Windows 2000 client problems and WUS!
www.wsus.info/index.php?showtopic=4529)

Restart Automatic Updates service

Inspect WindowsUpdate.log again

Optional: create a windows startup script to automatically delete WindowsUpdate.log

Related
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How to Enable “Group Policy Editor” (gpedit.msc) in Windows 7 Home Premium, Home Basic and Starter Editions?

[How to] Force a Wsus client to check for updates [and not wait for the scheduled time to come]
run wuauclt /detectnow will trigger the notification of downloading,and not wait until its detection cycle.