Two words: Norton 360
also u should clean your temporary files, your history, internet explorer cookies, try a different router, open up taskmgr see how much cpu and memory is being used.
I had this same problem. Found out my hp digital imaging proccess was creating 66 thousand temporary files into my windows temp folder. I used norton 360 startup manager to stop it from starting up on bootup. So it doesnt start up on boot which means its not on anymore.
P.S. if you dont know how to see your temp. open run and type %temp%
+rep me if this helped somewhat or solved your problem
EDIT: and if this does help solve your problem how much will you donate