Vista File Slowed To A Crawl

im a newbie to these forums and im a very inexperienced person with computers but here is my problem. My laptop became infected with trojans and spyware because of a doggy download which opened a hole for this stuff to spread. That rouge software winPc defender installed itself onto my computer. Although I was able to get rid of that pretty quickly and other stuff as well (using norton360, spybot and spyware doctor) that annoying "Insecure Internet Activity. Threat Of Virus Attack" message kept coming up, I also found that whilst using google i would be redirected to pages not relevant to what a had search for (such as blinkx or myspace video)

Using smitfraudfix I was able to remove that message But since I have used smitfraudfix my laptop has been running very slowly and has been crashing and failing seemingly at random. Whenever i try a google search on IE7 it still directs me to blinx and other places that I DID NOT type into the search engine and so I began to lose patience and I downloaded firefox3. Despite countless scans and checks nothing ever comes up so I suspect some spyware or malware may have sneaked its way undereath so that it is virtually impossible to detect.