i need help to remove Trojan_DNS changer and Trojan-downloader.popuper?

i download this game for my sister since she wanted it badly i scanned it but avast found nothing wrong with it then i installed it nothing bad happen but once my sis started to play all theses trojans warings and Adware came out with my avast i deleted them then spyware doctor told me it blocked trojans but i found i still have Trojan_DNS changer and Trojan-downloader.popuper i want to delete them i think that theres more but i dont know how to remove em all!!! help me plz

Use Malwarebytes Anti-Malware:

http://www.download.com/Malwarebytes-Anti-Malware/3000-8022_4-10804572.html?hhTest=1.

Download, install, update and select Full Scan.
Remove all infections that it finds after scan.

SUPERAntiSpyware Free Edition:

http://www.download.com/SUPERAntiSpyware-Free-Edition/3000-8022_4-10523889.html

Download, install, check for updates, then select Scan your Computer, select your drive and select Perform Complete Scan

Spybot S&D:

http://www.safer-networking.org/en/download/index.html

Download, install, update and Immunize, then click ‘Check for problems’ then when complete select all and then ‘Fix Checked’

VundoFix:

http://www.symantec.com/content/en/us/global/removal_tool/threat_writeups/FixVundo.exe

Disconnect your computer from the internet
Run vundo
Restart your computer
Run the tool again to ensure no traces are left.
If there are the reboot into Safe Mode and run FixVundo again.

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