PCs using Microsoft's automatic Windows update service will be checked for pirate versions of the operating system from today – and dodgy copies will be refused all upgrades except critical security patches.
Users will have the option, in a pop-up box that appears at the start of a scheduled update, to opt out of the validation, but they too will be refused full updates.
Validation under Microsoft's Windows Genuine Advantage (WGA) scheme is already necessary to get downloads of programs such as Internet Explorer.
Unvalidated users will also be nagged by a reminder box that appears at any time the automatic update procedure is run.
'You will be able to suppress the box but you will not be able to remove it,' said Michala Alexander, head of anti-piracy at Microsoft.
Users who fail the test can opt to go to a page explaining why and advising how to get a genuine copy of the operating system.
They are advised to contact their supplier if they bought the software in good faith, pre-loaded on a PC.
Alexander said this is the case with nearly one in 10 pirated copies and that it is not simply Microsoft that loses out.
Customers are being cheated because they are not entitled to full support, she added.
'And if Dodgy Dave is selling multiple copies of Windows on several machines he is undercutting genuine dealers,' she said.
A pilot of the validation system has been running in Norway and Sweden and is extended today to Britain, the US, Malaysia, Australia and New Zealand.
Launched today is a parallel scheme called Office Genuine Advantage which will validate Microsoft Office code.
This will be completely voluntary at the start but is expected to go the way of WGA by being linked to automatic updates.
A similar scheme is being extended to Microsoft Office installations but it is not clear whether this will be voluntary.
Alexander said: 'Our aim is to educate our customers about the risks associated with using counterfeit software and equally, the value they can gain from ensuring the software they are running at home and at work is genuine.'
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