Not receiving any packets???

I have a adsl. My computer uses a network cable and connects to a four-port adsl modem. However I am unable to browse the internet, no pages load, I cannot use msn... it never connects, I cannot even see others on the network anymore.
I know nothing is wrong with the modem bcoz there is another machine in the house that uses it and is working perfectly.
When I look at the networking icon in the taskbar it rarely blinks, and sometimes it does not receive any packets.
I don't think I have a browser hijacker... I've already tried using Spy Sweeper, Spyware Doctor, Trojan Remover, Spyware Eliminator, Counter Spy and Microsoft Anti-Spyware.

Could be a problem with your router...have you tried plugging the computer into another port and used a different network cable? Your network card in your pc might be dodgy, so that's something to check out. Also have you got your firewall set correctly, i.e. not on "lockdown" security where nothing comes in, and nothing goes out?

found the problem. it was zone alarm... I was attempting to install it and it didn't install properly. However one of its processes was running in memory. Once I got it reinstalled it worked.

Ah right, okay...