I assume these are Flash games? One of the differences between Windows XP and later versions of Windows is that the Flash player plugin on Windows Vista-7-8 has an additional feature called Protected Mode. This feature helps protect your system from untrustworthy Flash media by splitting it up into multiple different processes in memory. This works fine on some systems but causes serious performance issues and even crashes on other systems. I suggest disabling the Protected Mode feature of the Flash Player plugin to see whether that helps. This involves creating or editing a settings file. The following pages/posts provide different ways to do that: * Adobe support article under the heading "Last Resort": [http://forums.adobe.com/message/4468493#TemporaryWorkaround Adobe Forums: How do I troubleshoot Flash Player's protected mode for Firefox?] * Manual steps: https://support.mozilla.org/questions/968190?page=5#answer-509209 * Batch file to automate the manual steps: https://support.mozilla.org/questions/982093#answer-518078 Flash needs to completely unload from memory (restarting Firefox might help) before this would take effect. Any improvement?