If your PC starts to do strange things and behaves oddly, it´s more than probable that you have some kind of malicious element inside. In these cases you need a versatile and complete tool like WinFortress 2.3. It detects, identifies and destroys viruses, spyware, malware, keyloggers, trojans and adware, cleaning not only the hard drive but also the Windows Registry.
It also comes equipped with a tool to deny access to all software that cannot be fully trusted, and manages a list of programs that install on Windows startup.
To work correctly it needs NET Framework 2.0 or later previously installed. If you don´t have it you can get it here:
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Link.