I use Firefox almost exclusively on my ancient computers. Everything works fine for me. You might want to open Firefox, goto the tools tab and see if you have any errors in the error console. If so, then let us know of goto the Firefox forum and see if there are any resolutions. My pc parameters are: 1.4 GHz Athlon, 3 GB RAM, 512 MB Geforce 6200 PCI video card. Also, what add-ons do you have added into Firefox, if any ?? Ad blockers would potentially prevent the videos from playing/ showing.