I think OP forgot to write or paste any link here. May be some dangerous viruses attaced his PC. - Digital -
Jerusalem - 1988 This is one of the first MS-DOS viruses in history that caused enormous destructions, affecting many countries, universities and company worldwide. On Friday 13, 1988 the computer virus managed to infect a number of institutions in Europe, America and the Middle East. The name was given to the virus after one of the first places that got "acquainted" with it - the Jerusalem University.
Morris (a.k.a. Internet Worm) - November 1988 This computer virus infected over 6,000 computer systems in the United States, including the famous NASA research Institute, which for some time remained completely paralyzed. Due to erratic code, the worm managed to send millions of copies of itself to different network computers, being able to entirely paralyze all network resources. The damages caused by the Morris computer virus were estimated at $96 millions.
What about that recent one said to have infect tons, what even happened to it anyways? Can't remember it's name.
The latest and most dangerous virus : "Downadup" - 2009 The latest and most dangerous virus is the "downadup" worm, which was also called "Conficker". The computer security company F-Secure stated that the computer virus has infected 3.5 million computers worldwide. This malicious program was able to spread using a patched Windows flaw. Downadup was successful in spreading across the Web due to the fact that it used a flaw that Microsoft patched in October in order to distantly compromise computers that ran unpatched versions of Microsoft's operating system. But the greatest power of the worm is believed to be the ability of computers, infected with the worm, to download destructive code from a random drop point. F-Secure stated that three of the most affected countries were China, Brazil and Russia.
The Most DANGEROUS VIRUS IN HISTROY IS.... drumroll please! AMERICA ONLINE! AOL deep rooted itself into every copy of Windows and is next to impossible to uninstall 100% due to AIM and deep rooting to your network adapters at which it would mess up.
Nimda - 2001 Shortly after the September 11 tragedy this computer virus infected hundreds of thousands of computers worldwide. Nimda was considered to be one of the most complicated viruses, having up to 5 different methods of infecting computers systems and duplicating itself.
A dangerous Trojan spying on your computer while connecting to a remote attacker is a threat big enough, in itself. What if the same malice has peer-to-peer creeping ability too?! Exploiting Windows vulnerabilities, this worm will proliferate in networks. First it copies itself into a shared folder on the local machine. From there, the P2P network takes over to contact other computers in the network and helps them download and execute the infected file.