I had the same problem with the internet, and i'm not on a dell, I have a HP Pavilion dv4-1412la, I tried all the things that you can imagine but nothing resolved the issue, I had to restore the pc to it's factory settings by formating it and reinstalling everything. That solve the issue.... but I knew that it was something that could have been solved in way less radical. After all this I figured out that the problem was not due a spyware or any kind of virus, it was due to a P2P program called Ares, i'm not telling that this software is a malware or dangerous in any kind of way, but a friend of mine told me that he had the same problem and when he was running ares the browsers won't work but when he restarted the pc and closed ares the browsers worked fine, I tryed that on my laptop and it was true (at least in my case). So if you have any p2p software running try to close it, unmark it from the start up (you now.... type msconfig on the run menu......) and restart the pc, if the browsers woork fine Voila!!. If that's the problem and you still want to use the p2p software I think that you'll have to see if maybe the p2p is having any problems with the ports; if thats the case just give to it any other port and make sure that you open that port in your modem.
I hope this help you anyhow