Windows 10: suspicious Windows.old file

I have a custom built computer that has only had W10 on it. 2 weeks ago I couldn't get on the Internet and it took several techs to figure out why - it was some kind of malware that didn't show up in any scans, put "Killer" in the systray and popped up a screen showing SoundBlaster. The tech didn't think either one was legitimate. Both were installed the day the computer went down and when they were removed, things seemed fine. I have had 2 BSODs since that said "Bad Pool Leader" and today I noticed I have a huge file in my C drive, "Windows.old", which was created that same day. Since I have never had an upgrade, I know this isn't a normal Windows file. Can I delete it without a problem?
Thanks for any suggestions.

:)

 

Suspicious 2.6GB file in Windows.old

Please see:

https://support.microsoft.com/en-za...-996f-99e02c7301c2/disk-cleanup-in-windows-10

"select Clean up system files" ->check the all the boxes

There are instance when 'Disk Cleanup", does not remove the Windows.old completely, please post back if Windows.old still exists after running Disk Cleanup (Clean up system files). Please let me know the subfolders (if only a few) of the Windows.old folder
(is the file in question in a subfolder?), after running the tool.

Do you use OneDrive,
FileHistory, or something else to backup your data?

▓►Avoid a post. Backup your data.◄▓-{from the signature of Bruce Hagen(MS-MVP)}

 

Suspicious 2.6GB file in Windows.old

Windows 10 Single Language (Build 15063.447)

Acer Swift 5 (SF514-51-530G)

 

Actually, Windows.old is created not just when you upgrade, but also with some large updates. For instance, the Windows 10 November update creates a Windows.OLD folder when it is installed.

So depending on how long it has been since you let Windows Update install patches, this folder is probably normal. I would recommend running "disk cleaner" and selecting to remove the Old Windows Installs from the options. You may have to select the "Clean System files" button to get there.

 

Try using the Disk Cleanup utility, and after it makes its first pass over your boot/sys drive, tell it to "Clean up system files." Normally, this will get rid of Windows.old in a jiffy. If that fails to clean things up, let us know here and tell us how big the folder remains. If it's under 0.5MB it's probably nothing to worry about. Bigger, though, and things might get interesting.
Good luck!
--Ed--

 

Thank you so much. I did run the "clean the system files" and it got rid of it - it was a huge file so now I have a lot more room. It was sort of unnerving not to really know what actually that malware was or what it did though.

 

Glad it worked for you. If you want to read about how I dealt with a remnant of Windows.old that the utility failed to cleanup, check out my blog post entitled "Temporary Files Cleanup: Build 1429" posted Monday, 3/21/2016. Essentially, I had to take ownership of the holdout directories, and then delete them manually, one at a time, working up from the bottom of that folder hierarchy.
HTH,
--Ed--

 

Thanks so much - I'm going to look at that.