Are you sure you don't have a virus? Some of the symptoms you describe can be attributed to viruses. If you have a top tier antivirus program, update the definitions and run a scan. If you don't have a top tier antivirus program, download Malwarebytes and run a scan. It couldn't hurt.
It might not help, either. Here's why:
Most MS-Win users run with Administrator privileges. This is the same as operating as "root" on a Unix system. It gives whomever is running, and whatever they're running, free reign over the system to read, write, create, delete, modify whatever desired--incl. the files that make up the system, itself. So really good virus', worms and Trojans modify parts of the system in such a manner so as to hide themselves from anti-malware scanners or even fake updates to them.
The only two certain
ways to clean a system are:
- "Nuke and pave": Reformat the drive and re-install from scratch. Any backed-up data you wish to restore must be scanned by a competent and up-to-date scanner before being returned to the re-virginized system.
- Scan the MS-Win partition from outside it. I boot from a Linux "live" CD and run an updated copy of ClamAV against the MS-Win partition.
That being said: What will often work, but is far from guaranteed, is to reboot the system into safe mode with networking, get updated versions of multiple anti-malware programs, and delouse the system from there.
At this point I'd normally give my usual speech about not running with Admin rights and not using any more MS malware than absolutely necessary
, but I've learned such advice is generally futile, so I'll not bore y'all with it.