Whatever brand PC you got, go to their website and download the appropriate drivers. You probably never did this the first time. Vista likely picked the "ideal" drivers it thinks your computer needs which slows it down because they are not optimized for your hardware.
You need your PC brand and model, then go to the support/downloads section and update. Then go to the windows site and get those updates. Whenever I start fresh I have the same issue.
Also, when loading websites computers normally save much of the data in the cache to speed up the loading process. You deleted your cache when you started fresh, so the first time you visit sites it will take a little longer than normal, after that it should speed up.
I hope this makes sense, I have
indulged tonight.