Coputer bogged down by windows os

hi..
i had a windows vista on my laptop before... there was some problems with it as in it used to boot very slowly and the programs too used to open up very slowly even after it booted up... a deep virus scan from eset smart security showed nothing..

i got a windows 7 upgrade dvd for a small fee and installed it after completely formatting my entire hard disk..
the problems still persist...

very slow boot up..
programs take a long time to open up...
the whole thing just is damn slow..

my config:
intel core 2 duo 2.0 ghz
3 gb ram
320 gb hdd

its a compaq laptop..

any insight as to what i can do to make it better is highly appreciated