Please consider turning on send info to Mozilla from within Firefox before posting. No info = guessing. Please update to version 57.0.2 https://support.mozilla.org/en-US/kb/update-firefox-latest-version If still issues : You could try this please : Go the Menu then Tools --> Options --> Performance and untick everything. change the recommended size lower then see how it runs. Note: 0 = No Multiprocessor = slow again. TRY 2 Restart Firefox after making these changes please. Run Windows Disk Cleanup. Then run it again and click the button that says Cleanup System Files. Note : this program should be Pinned and run weekly, if have never done 2nd one expect 10's of gig's. Defrag Uninstall all Dell Bloatware installed when got the cpu. Go through Settings ever heading and turn off everything that do not use. Right click programs and see if will uninstall like Ms Support/Feedback. Empty Maps and turn off, use Google Maps instead. Go up the start Menu and Right click everything and some can uninstall. Just because can run Win10 does not mean you should with low system resources and low ram. Go through every article and see how it can help you : https://www.howtogeek.com/t/windows10/ Use this from stop sending massive amounts of data to MS https://www.oo-software.com/en/shutup10 Make a Folder on The desktop Run it from there, makes 1 file. Every up dates go get another new version and copy of top and run it. Please let us know if this solved your issue or if need further assistance.