How do you remove DNS malware from windows 7?

A friend of mine suggested that the reason why my computer was selectively accessing some internet applications on not others was due to something called DNS malware. I understand it is also hard to remove and virus checkers won't indentify it. Any tips for diagnosing if it is indeed the aforementioned? and if so how can it be removed without messing up my laptop? Please bear in mind I am competent with the basics but once it comes to fiddling with the internal workings of my computer I'm nervous and ignorant. Kiddy steps with explantions please!