Installing Windows 10 on a PC that is infected with malware

I am trying to fix a Windows 8.1 laptop that has been badly infected with malware.  Attempts to clean it have pretty much failed and so I've decided to reinstall Windows.

My preference would be to go straight to Windows 10.  However, the How to perform a clean installation of Windows section of says that to upgrade to Windows 10 for free, you need to use the Upgrade this PC now option.

Does this mean that I'm going to have to reinstall Windows 8/8.1 and then upgrade to Windows 10 in order to do a clean install of Windows 10?  Or is it possible to go straight to Windows 10?



Question Info

Last updated March 26, 2019 Views 1,514 Applies to:

Have you run a full scan with Malwarebytes and AdwCleaner?  I wouldn't proceed with anything except a Clean Install Windows 8.1  unless it passes those two scans until they come up clean. 

If these clean it up sufficiently then I think you'll be OK as long as you use the method here to make sure nothing is saved when doing the Upgrade: 

If confident your hardware is modern enough to meet the Windows 10 Specificationsincluding any unsupported OS features, then you can bypass Get Windows 10 app in the System Tray to Install  Windows 10 using the media creation tool choosing the first option to automate the Upgrade which overcomes almost all issues with Get Windows 10 in the System Tray.   


However in the same amount of time it takes to download that option, you can choose the second option "Create Media for another PC" to make bootable flash or DVD media to keep for any needed repairs or reinstall, and can be run from Desktop to Upgrade.  This media also gives you an extra option to "Save Nothing" during the Upgrade which overcomes Upgrade choking on corruption or bloated factory installs and gets as close to a superior Clean Install as an Upgrade can get. 


To run the Upgrade the media must be opened in Windows 7/8.1, then right click Setup file to Run as Administrator. 


 If asked do not insert a Product Key at any time, just click Skip or Next. 


If you want to  maximize chances for a successful Upgrade, then choose to Save Nothing so the Upgrade has much less to choke on and has less problems after install.  Make sure your files are backed up separately and you have your program installers and any Product Keys for programs like Office


To improve the Upgrade's chances turn off everything at Startup:


In Windows 7, type msconfig in Start Search Box, uncheck everything on Startup and Services tabs, but only after ticking the box in Services to “Hide all MS Services”.  Then click Apply, restart PC when prompted. 

Uninstall any anti-virus except Defender.  Bloated AV's like Norton, MacAfee, AVG and Avast need to have special Uninstallers (removal tools) for common antivirus software - ESET Knowledgebase.



It’s highly recommended to Create a backup System Image of your existing OS before upgrading, which can be recovered using the booted Windows installation media, Repair CD or Recovery flash drivein 20 minutes.   Type Backup in Start Search box, in Backup and Recovery Center choose Create a System Image.  You can also use a more flexible imaging program like free Macrium Imaging which allows recovery to any partition position on the hard drive.


Immediately after install, type Update in Start Search box to Check for Updates, expedite these through requested restart, then check again until no more are offered. 


Next right click Start button to open Device Manager, import any drivers still missing from the PC or Device's Support Downloads webpage.  How to: Install and Update drivers in Windows 10 - Microsoft Community


Stick with built-in Defender in Windows 10 for best performance and adequate protection.  If you get infected add the inexpensive Real Time protection from the best-in-class free malware scanner Malwarebytes. No one I’ve had do this has ever been infected again.  I'd also periodically scan with free Malwarebytes or AdwCleaner  scanners.

If any problems persist then after confirming Activation of Upgrade you can do a Clean Install Windows 10.  Always be sure with any clean install to delete all partitions during the booted install, using the Drive Options on the "Where do you want to install Windows?" screen. 


Feel free to ask back any questions and keep us posted on how it goes.

I am a volunteer and not Microsoft.

Over 100,000 helped in forums for 10 years. I don't quit for those who are polite and cooperative.

Windows MVP 2010-19

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