If you suspect Firefox is involved with that problem and is the only application causing that then for now stop using Firefox. Check how much free space you have on the hard drive both in terms of GB and as a percentage of the total size. I hope your backups are up-to-date, both in terms of sytem recovery, and any personal data.

It probably worth running chkdsk and defrag on the XP And the major disk suppliers usually provide utilities for checking the disk function.

There is the possibility that your disk is getting faulty, or full, there is also the possibility it is a malware problem, a noisy hard-drive with the computer locking up is not usually good news

That's the plan.... I have 2 80GB hard drives, both backed up and recently defragged. Appears that both are appx. 50/50 used/free.

I suspect its my pc and the newer firefox which is why I am considering going to the trouble to go back to the 3.6 version. However, it also seems to be a function of time, in that I have to have been browsing for awhile before it happens. Am leaving Task Manager open to see if I notice anything there.

I don't think it is a malware problem as it ONLY occurs when firefox is running.

Thanks for looking into it. I'll back it up again just to be sure.

Firefox 4 causing a computer to have hdd problems and to lock up would be a serious fault, that may have been expected to have shown up even prior to beta testing.

There will have been a few posts moaning about memory usage on firefox 4, and some about slow start up in some configurations, but looking casually at posts I do not personally notice hdd problems and lockups as being a problem being reported with firefox 4.

If the problem is only when firefox 4 is running it is, I would think, almost certainly going to be down to interactions with something else, other software / extensions. I have firefox 3.6 & 4 on XP and have not noticed any unusual problems.

Maybe the problem is unrelated to firefox, possibly the computer is fairly idle whilst browsing and some other activity is taking place, such as disk indexing or security scans. You can of course set Task Manager to display info that may be more useful than the default settings, if you are trying to prove what is using the hdd.

• Task Manager -> [Process {tab] -> View -> Select columns
  it does have a reasonable help menu

You also have a lot of options from Performance Monitor: counters graphs or logs, but you will need to read up on how to use it.

• Control Panel -> Performance and Maintenance -> Administrative Tools -> Performance

Of course with the millions of firefox users, some are going to have hdd problems. Hope you get to the bottom of your problem.

I also have the same problem for the exception I am running Windows 7 and it seems to only do this when opening a streamed internet video.

I have this problem too, and it's Firefox 4.0 causing this issue, since my computer does not locks up in any other way. When browsing pages (particulary Facebook), suddenly FF stops responding and then everything else crashes. Only way to recover Windows is by manually shutting down the computer. Event Viewer does not report anything unusual besides the fact that Windows did not shutdown correctly.

The only difference is that my harddrive does not make any noise when the lock up occurs, and the hdd light is off.

I have 2 addons in FF, NoScript and Adblock Plus. My PC has more than enough memory and harddrive available. I'm running Windows 7, x64, Ultimate.

That's why I'm probably going to make time next week to go back to 3.6.....

Thanks again. And I see there are a few others experiencing a similar issue, just a few...... Thanks again for looking into it.

@ cool1007 & jtill

I suggest you each start a new question about your own particular problems, you can always add a link back to this thread.

You may well however discover that you each have completely different causes of this problem.