Trojan.Win32.Agent.akk removal

I have been getting a box (looks like a windows system message) that pops up periodically and randomly on my screen that says my computer has Trojan.Win32.Agent.akk, then says to click below to get the software to clear the trojan (recommended). I can click "OK" or "No thanks" (I think - I only copied down the name of the trojan). Your browser was hijacked by Trojan.Win32.Agent.akk How to remove and clean system, please help! You need to clean your system immediately, in other case it can be crashed soon! Trojan is a general term for malicious software that is installed under false or deceptive pretenses or is installed without the user's full knowledge and consent. Most Trojans exhibit some form of malicious, hostile, or harmful functionality or behavior.