Constant Browser Crashes...

Hello MG... First time poster, long time fan.
A couple of weeks ago my firefox 3.0.5 crashed and closed with the error reporting window in the middle of a casual flash game (on a web site I've used without drama for ages). Since then it's been crashing repeatedly, at first only during games but, now, it happens whatever I'm doing online with a browser. and so does IE. I even downloaded and tried Chrome and it has the same trouble. It's not that I thought I could ignore the problem this way, I just got so frustrated googling and googling and still not finding a solution. For various reasons, I only have a dial-up connection at the moment and so multiply the frustration and time consumed by 50! I should also mention that I have Windows Xp Home and I'm using AVG 8.0.176 Free and the latest Zone Alarm Free.
I keep reading that I should update flash, update shockwave, update java, update the browsers and/or reinstall them all. I did this and the problem persists. If anything, it seems to have gotten worse with firefox crashing every hour or so, sometimes even more.
I noticed some hs_err_pid log files in the mozilla firefox folder, about nine of them in total. So, obviously, there's a problem there but I just want to point out that I've had many, many more than nine crashes.
I'd also like to throw in that my computer developed another problem roughly six months ago when it began rebooting itself (or trying to, instead I get the blue screen of death) in the middle of any kind of registry scan or virus scan. I haven't been able to find an answer for that either. I've tried so many spy/ad-ware scans and read countless forums but I give up. Obviously, I don't know near enough to figure or search it out with any success.
I'd be very grateful of any advice on where I should start in trying to identify and solve these problems...
Thanks for your time x

 

Thank you for the speedy response, Mark.
I'll get started on that right now.

:crap
(just wanted to see what that one looks like.Ha.)