I’ve recently noticed that when viewing pages with Flash content in Firefox 4 (such as YouTube or any page with a Flash advert) that my PC slows to a crawl. The Windows Task Manager shows that the culprit is plugin-container.exe. The idea behind plugin-container.exe is that Firefox runs all plugins in a separate container – so that if the plugin crashes, the browser itself doesn’t crash but stays open. In theory it is a good idea but it makes my PC unusable so the only way to go is to disable it.
Thankfully it’s not too difficult to disable – type about:config into the address bar, and search for ‘dom.ipc’.Then change the value for ‘dom.ipc.plugins.enabled’ from true to false (just double clicking on it should change the value).
Once this is done, restart Firefox and it will no longer use plugin-container. Now web pages featuring Flash no longer slow down my PC quite as badly!