|Did Combo Fix find anything?|
You don't have to pay for an antivirus. For example there is "Microsoft Security Essentials" or "Avast free version".
If you don't know where to find Microsoft Malicious Software Removal tool (see #4) then just type MRT.exe in the run box. This is only any good if you keep it updated and is no substitute for an antivirus.
MalwareBytes freebie can unearth some of the more difficult viruses, so install update and run that too. You can get it here:
Maybe your issue is not down to a virus but as you have not been using an AV then that is the first thing to check for.
Always pop back and let us know the outcome - thanks