A problem with Microsoft Windows caused sweeping outages affecting hospitals, airlines, emergency services and people at home. The error — caused by a technical problem with cybersecurity software from CrowdStrike — sends users to a “blue screen of death,” telling them their device needs to restart.

But simply restarting might not fix the issue, users report. On Reddit, IT workers discussed the dizzying scope of the outage.

“This is what Y2K wishes it was,” one user commented. Others said the outage was the worst they’ve seen and noted the multiple steps they’re taking to get their employers back online.

Microsoft and CrowdStrike blamed the outage on a CrowdStrike software update that went out Friday. In a post on X, Microsoft suggested that affected users fix their computers by restoring the system to a point before the buggy CrowdStrike update went out. It linked to online directions for a manual restore.

“Blue screen of death” is a cheeky nickname for a Windows error message that can keep users stuck rebooting their computers. The message reads “Your device ran into a problem and needs to restart. We’re just collecting some error info, and then we’ll restart for you.”

Most of the work of getting systems working again will fall to IT professionals working for organizations. But people at home can attempt to work around the blue screen of death as well.

“The worst thing that happens if you try fixing it is that it doesn’t work, so you’re back where you started,” said Gregory Falco, a professor of systems engineering at Cornell University.

The simplest fix is to repeatedly reboot your computer, said iFixit CEO Kyle Wiens. Try restarting up to 15 times to see if anything changes, he suggested.

If that doesn’t work, you can restore your computer to a version before the update. To do so, power on your PC, but before it can launch, press and hold the power button to turn it back off. Do this three times in a row, and after the third time, you should see some advanced settings appear. Go to “advanced options,” then “system restore.”

You’ll see options for different restart points. Choose a point before the blue screen appeared, perhaps from yesterday. Then click through to the end by choosing “next” or “finish.”

You can also trying booting your computer into Safe Mode. To do this, follow the steps above to power on and off until your screen shows advanced options. Choose troubleshoot > advanced options > startup settings > restart. Once your device restarts, select safe mode. Use the computer menu to find the folder C:\Windows\System32\drivers\CrowdStrike. Then find the file named “C-00000291*.sys” and delete it. Last, restart your computer.

If you can’t get through to 911 or other emergency services, check the websites and X accounts of your local police, fire and state trooper departments. Many should list alternate emergency numbers you can try.