My stepmother had a PC with the following specs:
OS: Windows XP Professional SP3
Security: McAfee (can't remember what version)
And had the latest updates
The year was 2010. Once she started the PC, she noticed that all icons on desktop and also all personal files had turned into .pdf files. What helped: Complete reinstallation, since she couldn't even use McAfee, because it had turned into a .pdf file.
OS: Windows XP Professional SP3
Security: McAfee (can't remember what version)
And had the latest updates
The year was 2010. Once she started the PC, she noticed that all icons on desktop and also all personal files had turned into .pdf files. What helped: Complete reinstallation, since she couldn't even use McAfee, because it had turned into a .pdf file.