HELP..Does anyone know about issues?

Does anyone have any problem with windows xp service pack 3.1? It seems to slow my computer down, or maybe it's something else. Also, what about Vista? Is that a good thing to download? My computer is normally very fast getting online, etc. However it has slowed down alot! And I'm not sure why. I have updated everything. Also web sites freeze and I have to X out or end task.. and seldom at times I log in to the internet and it will boot me out, and I have to re-enter which goes smooth after the second approch but after approx. 15 min. I lock up and have to end task...Any help would be Great appreciated! Hugs.....Connie