this sounds dumb , but , if you watch lots of streaming video like i do , you really notice it .
delete all your browser history , ( if you have google toolbar installed , delete browser history from the google toolbar , it seems on my computer it is seperate from the windows browser history ) make sure to TURN OFF ( save favourite website data )
go into the google toolbar settings and turn off all of the stuff you don,t want on
( which is almost everything ) it will be obvious .
then defragment the disk .
reboot your computer .
if that doesn,t help , recover your computer to a previous date when you know it was working good .
my general rules of thumb :
on any website that wants to install something to run something = NO
automatic windows update = bad ( better to select the updates yourself )
if your pc starts acting wierd when you are on it = hold down the power button till it shuts off ( don,t do a windows shutdown , it will save whatever is affecting your pc )
i,m far from a computer geek , but it seems to work for me