More then likely a virus if you already changed batteries.
To be sure, you can grab an old plug in and try that.
If a virus, you need to get some scrubber software.
There is spybot, adaware, and others you can google up. Many are free, some work, some don't.
Get your pics, files etc backed up also in case, you have to restore your OS.
Before you do that though, try the cleaners and also see about your last OS restore point and see if you can back up to that point