With less than a month to go before the Windows 10 free upgrade offer comes to an end, Microsoft is making a last-minute push to convince users of its older operating systems that they really would be better off making the move to the latest OS.

Microsoft has gone all out with this final piece of nagware. If you thought the previous upgrade notifications were invasive, wait until you see the full-screen, purple announcements that are appearing from now until July 29 – the day the free Windows 10 offer ends.

The new prompt may take up your entire desktop, and some users could, on first inspection, mistake it for the blue screen of death, but at least Microsoft starts off with an apology. “Sorry to interrupt, but this is important,” it states, before advising people to upgrade.

Windows users can choose to upgrade straight away, be reminded later, receive three more notifications, or never see the prompt again.

There will be some Windows 7 and 8.1 users who never see the full-screen alert, including anyone who has previously selected the ‘Do not notify me again’ option, those who upgraded and rolled back, and people with a computer that is detected to be incompatible with Windows 10. Additionally, the prompt won’t appear if you have a recent version of the “Get Windows 10” app installed.

Microsoft has received endless criticism for its aggressiveness when it comes to making Windows users upgrade. The company was accused of using “malware-like” tactics when it was discovered that clicking on the red x in a pop-up’s window was being considered as consent for the upgrade to take place. And last week, a woman was awarded $10,000 through a lawsuit that alleged the forced installation caused her PC to become slow and unusable.

There have been incidents where the prompts made some very public appearances, such as the live weather report and the Counter-Strike Twitch stream that were interrupted by the upgrade window. But they're set to disappear for good in a few weeks time, and anyone who wants to upgrade after this point will have to pay $199.