How to tell if something is wrong?

I don't know how to tell if something is wrong on the computer. The only thing I did recently was that Msn Messenger issue, but I got rid of it. And lately...(on dsl) same Dell computer. The browsers and such is like freezing like it would if it was low computer and you were running a high running game. Its not "laggy" it freezing now. Id be running minor music thing and open this site and site freezes... Show in top left corner of Firefox white box or whatever(meaning it freezing atm).. cant click into anything.. Just have to wait.. And most the time I have to ctrl alt delete and close out of firefox or whatever I am doing because it 3/4 wont unfreeze. So I don't know if something inside is going out? I dont know anything about testing and replacing if needed other things then What I learn on adding RAM. So if you got any suggest remember I am dumb. K thanks Oh yeah incase you ask. Hm dell computer Windows XP home edition sp3, high speed internet, Firefox and IE 7(both freeze).

 

Yeah I just ran the stuff to make sure and its okay with malware and etc.. Also nothing is running.. cept computer and firefox. But it just keeps freezing. Like I don't know what else to tell you. Like I open firefox and have a little window for music playing a song. And both will just freeze. I try clicking on firefox (this site) to go to it and its just frozen. And says in top left like a white box or something. What I would compare it to is laggy but frozen. Like if you do to much your computer cant handle. But thats not the deal. I got new RAM and worked fine with it for month or so. It only starting happen recently. And my computer shows its reading the correct RAM that I installed while back.

 

MGTools added

 

I've had occasional issues with FF using too much memory. This is over a span of several machines and OS's. I am now running 14 tabs and 200MB and it's fine but if it gets much over 400MB then I get some serious lag and freezing.

All I do is cancel it from Task Manager to preserve my tabs and then I re-open FF. At that time it goes back to 100MB which is normal to have with the same tabs open. I'm not saying that's your issue, but worth looking at. Also I only have a couple of add-ons.

 

my firefox is 60k atm.