"Security Antivirus" has hijacked my system.

Hi guys, Please help me on this!
i recently gave my laptop to someone for some work and wen it came back, there's this thing called security anti-virus running on it. i don't know how it came about but it's some strong Troja horse, i think.
It has taken control over my anti-virus program (avira), and i can't even install AVG internet Security (it's saying saying "setup can't continue due to a driver problem.
Anyone can help me?

[sparkax]

First of all-can you uninstall Avira?
Whatever,try installing AVG in safe mode.

I uninstalled avira, let me try and see if AVG can install in safe mode.
Thanks.

Installing AVG in Safe mode has failed too. It's telling me to restart and after restarting (still in safe mode) it says that AVG was successfully installed but when trying to run it can't!

[mcmike]

Read this. Security Antivirus removal instructions:
http://www.bleepingcomputer.com/virus-removal/remove-security-antivirus
http://deletemalware.blogspot.com/2010/02/how-to-remove-security-antivirus-fake.html

This should work!! thanks man.