Laptop freezes

Hello,
I've got a Packard Bell laptop with Vista home basic and 1.50 RAM (came with only 1).
Every single time I go onto a certain mobile phone ringtones website the whole thing freezes. i never used to have this problem,it's only happened over the past 12 months or so. A well known PC company had it for a couple of days due to a firus and took it back to "factory settings" and it's not been right since.
HELP!!!!