A few weeks ago, I noticed that I no longer had a working copy of Malwarebytes. I had in the past used this free program and was very happy with it. I decided to reload it, and somehow I got into a free trial of their premium program. That program almost wiped out my computer speed wise. Everything was running at about 1/5 th speed. Terminated it, and I’m back to normal. Windows 7 Professional, Firefox browser.
That's a good combo.
I've got Windows 7 Ultimate and Firefox on my desktop machine and it's as solid as a rock. I don't think I've ever gotten a BSoD on that device, nor do I ever recall Firefox crashing.