Firefox is more made for the modern PC. Since you are still running Flash 15 then I can see a large tech gap. Just because you can run Windows 10 does not mean you should. Below you will find information curb high ram and cpu usage : Please : go to the Firefox 3 Bar Menu --> Options --> Privacy & Security panel and under Permissions check (put a tick in the box) the setting to Prevent Accessibility Services from accessing your browser. Monitor in Task Manager. Should stay below 2 gigs. If excessive then do below and monitor and change if need to...Test and go up again , go back down, it will eventually get a zone you and it can live with. Go to the 3 Bar Menu then Options --> General --> Performance and untick everything. change the recommended size lower then see how it runs. Note: 1 = No Multiprocessor = slow again. Try 2 Restart Firefox after making these changes please. Flash 15 is so old and a security risk in the thousands you need to use this to uninstall it please : https://helpx.adobe.com/flash-player/kb/uninstall-flash-player-windows.html For Firefox Only : Flash Player Version: 28.0.0.126 Current Version https://get.adobe.com/flashplayer/otherversions/ Step 1: Select Operating System Step 2: Select A Version (Firefox, . . . .) Note: Other software is offered in the download. <Firefox on Windows Only> Please let us know if this solved your issue or if need further assistance.