[Shasown]

What version of windows do you use? If its XP make sure you have updated it to SP3, otherwise the latest firefox wont work properly.

What version of firefox?

When was the last time you cleaned and sorted out your registry.

On Tuesday/Wednesday what did you update/upgrade, install or uninstall?

An IRQL not less or equal problem is normally caused by device criver errors, BIOS probs or incorrect/incomplete upgrades. It often happens when people only occasionally upgrade windows XP consequently they do it piecemeal, often missing out vital updates etc.

Auto update windows, via the MS website and in future leave autoupdate ON, if it still shows it may sometimes with older computers (Intel 386s etc) be necessary to reinstall windows then directly update it to sp3 via the MS website.

After updating windows reinstall devices then go for the latest versions of browsers , antivirus etc.