Unfortunately, it seems that you downloaded and installed some spyware - namely SpySherif!
Get some decent anti-spyware software (I use Spybot Search and Destroy, and Spyware Blaster) which you can find on google, and they will probably solve your problem.
I am guesiing that you use AVG antivuris as AvgemC is part of that, so you will also probably need to re-install AVG.
The lesson to learn here is that just because something claims to be anti-spyware, that doesn't mean it is!
If ever I find any software that I think may be useful, I always Google the name first to see if there are any bad reviews, warnings etc.