Users of some VG and Avast antivirus software may be prevented from upgrading to the latest version of Windows 10 due to a compatibility issue. 

Microsoft has blocked upgrades to both Windows 10 versions 1909 and 1903 for AVG and Avast users running version 19.5.4444.567 or earlier. 

"To safeguard your upgrade experience, we have applied a hold on devices with affected Avast and AVG Antivirus from being offered or installing Windows 10, version 1903 or Windows 10, version 1909, until the application is updated," Microsoft says. 

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To get around the block, users will need to download and install an updated version of Avast or AVG. 

The updates and installation instructions for updating the antivirus software are available on Avast and AVG support pages.  

While this is the first time Microsoft has reported a compatibility block for AVG and Avast, some users have reported being unable to install version 1903 since August. 

Avast acquired AVG in 2016. AVG's page notes the block affects AVG Ultimate 19.5 and lower, AVG Internet Security 19.5 and lower, and AVG AntiVirus FREE 19.5 and lower. Avast products affected include Avast Premium Security 19.5 and lower, Avast Premier 19.5 and lower, Avast Internet Security 19.5 and lower, and Avast Free Antivirus 19.5 and lower. 

Microsoft has also imposed a compatibility block on Windows 10 updates for versions 1903, 1909, and 1809, due a compatibility problem with certain Qualcomm Wi-Fi drivers. Affected users should see a message in Windows 10 Setup that draws attention to the need to update the driver. 

"To safeguard your upgrade experience, we have applied a hold on devices with affected Qualcomm driver from being offered Windows 10, version 1809, Windows 10, version 1903, or Windows 10, version 1909, until the updated driver is installed," Microsoft explains in a support page.

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Windows 10 users should be offered a Qualcomm update after selecting Check for Updates, but if the update isn't offered, Microsoft has instructions for alternative steps should the updates not be offered automatically. 

"After you have updated your Qualcomm Wi-Fi adapter drivers, the safeguard hold should be removed and you should be able to install the newer version of Windows 10," Microsoft notes.