Acer Apire One 751 Very slow

Hello,

I bought an Acer Aspire One 751 with Vista Basic (1.33GHz - 2GB RAM). And I think it is very slow! It takes a lot of time to load firefox and surf the internet. Even when I click on "start" it takes time. I use it for work. When I use firefox and word 2007 at the same time is not possible. Moreover, the screen is a bit "noisy" (I can the some kind of lines).

How can i make it work faster?

Thank you for your help!