Did you install windows yourself?
If so, did you do it like this:

  • Disconnect from the Internet (pull out the cable)
  • Install windows (format the drive ofcourse)
  • Install ALL drivers for your system
  • Install avast
  • Connect to the Internet
  • Install all updates security/drivers (especially the security updates/service pack)
  • Install the applications you are normally using
  • Make settings/configurations changes is you want/need
  • Create a image of that drive

That last one will safe you a lot of time in case you need to/want to reinstall windows again.