My 4+ year old Toshiba Satellite runs XP and Firefox, but I also have Chrome installed.
It has slowed down quite a bit and has numerous problems such as audio stuttering. I am too old and stupid to know how to fix it, despite running all the normal maintenance and cleanup programs.
I just bought a used Toshiba, from a distressed expat, for my 18 month old boy to watch his U-tube kiddie spots. He already knows how to turn it on and work the up/down keys.
It runs Windows 7, which is a pain for me.
Make a backup copy of all your data files. Then re-install Windows XP from scratch. It will then run as good as new, unless you have hardware problems such as corrupted files on hard drive. Run CHKDSK program to cleanup bad sectors on hard disk if any.
I had the same problem and solved it by downloading an earlier version of Adobe Flash Player.
If you have auto-update for the Adobe Flash player, you update when reminded by Adobe that there is a new version. This problem may be inherent in the newer version. At least it was in my case.
Uninstall the Adobe Flash player on your system and install a previous version and your problem may be solved.
Are you referring to youtube.com or utube.com? They are two different websites.