My laptop keeps freezing once I use certain programmes how can I overcome stop?

My Acer aspire 7520 has windows vista home premium. It keeps freezing when I am on positive programmes. The blind goes each fuzzy and the cursor turns into thing that looks like a saw. I can nonmoving decision the cursor but the surface is fuzzy. When I click the stale button on my laptop the screen dims and the comes back on top of but the cursor isn't there. So I then have to click the button again and restart my laptop. This only happens once I am on certain programmes.