Q: I bought a brand new iMac at Apple Store in Cambodia

You are entitled to 90 days of free support with your purchase, I suggest you use it.

Your computer is covered by a 1 year warranty. Contact the store (not a genuine Apple Store) and let them know about the problem you are having.

Question for you....did you install any antivirus or cleaning applications????/

Do you mean Adware Medic?

mrnicoo wrote:

 

I bought a brand new iMac at Apple Store in Cambodia

There are not Apple Store's in Cambodia. Not run by Apple, at any rate.

Take it back to wherever you got it for service.

Adware Medic is fine. Take it back to the store you bought it from and ask about warranty service. Ask them specifically if they are an Apple Authroized Service Provider. If they are ask to see their paperwork proving they are.