Somehow ad-aware misses.. try Spybot Search and Destroy (as mentioned by slick 8790). I personally use these two! There are spywares spybot can get rid of which ad-aware cannot and vice versa.
These hijacking problems are very common when you visit porn sites...(so i guess if you dont want to be hi jacked avoid these pornsites!)
Try hijackthis (as mentioned again by slick 8790) to prevent hijack from taking in the first place!(its a freeware)
Also ever heard of anti trojans? The Cleaner by Moosoft is a good one!