Virus on non-updated Windows Vista PC that eats files off USBs?!

My man is having a very odd business with his PC. He's been trying to update it from Windows Vista (tee hee) to Windows 10. This won't work for some reason, although he does have a legitimate copy of Windows 10 that we bought from Staples. I want him to update but he felt he was being a rebel and I said I think that he's caught a virus from before Covid, since that's how long it's been since he's been online with this particular PC.

The virus or glitch is when I try to provide him with a PDF (.pdf), Word (.docx) or Notepad (.txt) file via his or my USB, the file is immediately deleted?! It's only deleting the new files, for all the old files are still on both our USBs and fine, but it's the darnedest thing that his PC is literally eating the files?

Luckily, it must be local to his PC because it's never happened to anything on mine, but the question is, how do we eradicate this virus, Trojan, or worm?

Will updating him to Windows 10 help? If so, how does he make the monumental leap from Vista to 10?

We have the latest Office365 for 5 devices and pay a pretty penny for that each year, so it's not versions or out-of-date there.

Hope there's some knowledgeable person out there that can help with this. For now he's stuck in the Vista limbo whilst I'm trying to help out, probably at risk of my own PC being infected (?)

Thank you in advance to anyone who may be able to help here.

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Answer

Great White North

The virus or glitch is when I try to provide him with a PDF (.pdf), Word (.docx) or Notepad (.txt) file via his or my USB, the file is immediately deleted?! It's only deleting the new files, for all the old files are still on both our USBs and fine... how do we eradicate this virus, Trojan, or worm?
Will updating him to Windows 10 help? If so, how does he make the monumental leap from Vista to 10? ...

Hi AwmostDone:

Assuming your friend is still using Vista and hasn't tried the upgrade to Win 10 yet, what antivirus are they currently using? There are very few antivirus programs that are still compatible with Windows Vista - for example, Panda Free Antivirus v22.x, Avast Free Antivirus v18.8 and Norton Security v22.15 (a paid product that requires purchase of an annual license). I believe Panda Free Antivirus is still fully supported on Win XP and Vista and a paid version with extra features like a firewall is also available, but Avast Free Antivirus v18.8 and the paid Norton Security v22.15 (Norton Smart Firewall included) are older legacy editions for Win XP and Vista that were released years ago and now only receive malware definition updates.

NOTE: before you install any antivirus on a system the old antivirus should be completely wiped off the system with the manufacturer's removal tool.

The legacy Malwarbytes Free v3.5.1 for Win XP and Vista (released May 2018) is a reputable on-demand anti-malware scanner (i.e., it does not load at Windows startup and provide real-time protection like an antivirus) that is available for download from https://downloads.malwarebytes.com/file/mb3_legacy and will not interfere with your antivirus. Malwarebytes Free v3.5.1 still receives malware definition updates but some Win XP and Vista users have recently reported issues keeping this legacy v3.5.1 product updated with the latest available malware definitions - see anon743's Sep 2023 Malwarebytes 3.5.1 not updating definitions... again for one example.

What default browser (please include the name and current version) does your friend use on their Vista machine, and are they able to download and save .PDF and .TXT files from the internet?

I agree with Bill Smithers' comments about how inadequate Microsoft's minimum system requirements <here> for Windows 10 are. I know of few users who were able to upgrade from Vista to Win 10 (in most cases these were custom-built systems with higher-end specs that were used for gaming) but in many cases system performance with Win 10 was so poor that they downgraded back to Vista.