If you are experiencing this problem right at this moment, perhaps ComboFix will be able to solve it.
Features and Highlights
ComboFix lets you run it without installation.
It is advised to close all running apps before you roll running ComboFix to scan your machine for malware.

ComboFix backs up the registry and creates a system restore point before it begins the scan.
If ComboFix finds a threat, it removes the threat automatically.
Occasionally you might find one or two threats that ComboFix fails to get rid of.

Perhaps this free malware hunter will come handy some time in the future.
An antivirus that provides a real-time protections is, therefore, necessary.
But even the highly regarded brands cannot deal with every kind of malware.
There are too many malware out there.
Home users, who are not tech savvy, are not recommended to use it though.
It is best to leave the job to those who know what they do.