Flawed AVG antivirus update cripples Windows XP PCs

Deletes critical 'user32.dll' system file, blocks booting

A flawed signature update to AVG Technologies' antivirus software over the weekend crippled some Windows XP PCs by mistakenly deleting a critical system file, the company has confirmed.

According to messages on AVG's support forums and its own support site, an update released late Saturday for the company's security software fingered the "user32.dll" file as a Trojan horse. As per the program's settings, the AVG software, including the newest version 8.0 and its predecessor 7.5, shut the .dll away in quarantine. The result: A crippled computer.

The problem only affects users of the Dutch, French, Italian, Portuguese, and Spanish language versions of Windows XP.

"If you have chosen 'heal' or 'quarantine,' your PC will no longer restart," said a panicked user named "pa3bar" in a message Sunday. "It shows a blue screen at start up and tells you it cannot find winsvr, error c0000135. System recovery has no effect."

The problem only affects users of the Dutch, French, Italian, Portuguese, and Spanish language versions of Windows XP, according to the company. English versions of AVG are not affected.

AVG, best known for its free Antivirus, confirmed the error in a FAQ on its support site. "In case you are not able to run your Windows XP operating system after AVG 8.0 virus definition update, it may be caused by a false positive on a specific 'user32.dll' system file," the company said. "The file was moved to the AVG Virus Vault and deleted. Therefore it is not possible to start Windows."

Although some systems refused to boot, others rebooted endlessly instead.

On its support site, AVG posted instructions for affected users that involved running Windows XP's Recovery Console, disabling several AVG services and restoring the user32.dll file by copying it from the operating system's install CD. For users unable to locate their installation disc, AVG offered a utility that fixed the problem; those users also needed to create a bootable CD or USB drive.

The utility work-around was for AVG Antivirus 8.0 only; a similar utility for AVG Antivirus 7.5 will be available "soon," according to a message posted by a support forum moderator Tuesday.

An AVG technical support representative provided more detail on the snafu. "We can confirm that it was a false alarm," said Zbynek Paulen, who identified himself as an AVG employee. "We have immediately released a new virus update (270.9.0/1778) that removes the false positive detection on this file. Please update your AVG and check your files again."

That suggestion, however, only worked if the user had not turned off his or her PC, or rebooted it, in the meantime.

Join the newsletter!

Error: Please check your email address.
Rocket to Success - Your 10 Tips for Smarter ERP System Selection

Tags AVG

Keep up with the latest tech news, reviews and previews by subscribing to the Good Gear Guide newsletter.

Gregg Keizer

Computerworld
Show Comments

Cool Tech

SanDisk MicroSDXC™ for Nintendo® Switch™

Learn more >

Breitling Superocean Heritage Chronographe 44

Learn more >

Toys for Boys

Family Friendly

Panasonic 4K UHD Blu-Ray Player and Full HD Recorder with Netflix - UBT1GL-K

Learn more >

Stocking Stuffer

Razer DeathAdder Expert Ergonomic Gaming Mouse

Learn more >

Christmas Gift Guide

Click for more ›

Most Popular Reviews

Latest Articles

Resources

PCW Evaluation Team

Edwina Hargreaves

WD My Cloud Home

I would recommend this device for families and small businesses who want one safe place to store all their important digital content and a way to easily share it with friends, family, business partners, or customers.

Walid Mikhael

Brother QL-820NWB Professional Label Printer

It’s easy to set up, it’s compact and quiet when printing and to top if off, the print quality is excellent. This is hands down the best printer I’ve used for printing labels.

Ben Ramsden

Sharp PN-40TC1 Huddle Board

Brainstorming, innovation, problem solving, and negotiation have all become much more productive and valuable if people can easily collaborate in real time with minimal friction.

Sarah Ieroianni

Brother QL-820NWB Professional Label Printer

The print quality also does not disappoint, it’s clear, bold, doesn’t smudge and the text is perfectly sized.

Ratchada Dunn

Sharp PN-40TC1 Huddle Board

The Huddle Board’s built in program; Sharp Touch Viewing software allows us to easily manipulate and edit our documents (jpegs and PDFs) all at the same time on the dashboard.

George Khoury

Sharp PN-40TC1 Huddle Board

The biggest perks for me would be that it comes with easy to use and comprehensive programs that make the collaboration process a whole lot more intuitive and organic

Featured Content

Product Launch Showcase

Latest Jobs

Don’t have an account? Sign up here

Don't have an account? Sign up now

Forgot password?