Just some suggestions.. Any type of video can bog down if your net connection isn't getting the data to your computer fast enough. What type of internet connection are you using? IN addition, if you've only got 512 MB of memory and your video card is an integrated version, you may be running out of video memory.
Tried increasing the RAM?
Tried temporarily shutting down other resource hungry programs while watching the videos? Like your antivirus, etc.?
And if the computer is heating up during your use of videos, the processor may be balking at the increased work.. Try removing the computer case, then use compressed air to blowing out all the dust and junk from around the processor, heatsink, power supply, and all the fans.
Hope this helps.
For a while now I've had a problem with Flash. Whenever I use it for more than say 5 minutes or so, it causes memory usage to soar (above 100,000 K when I'm using Firefox). At first I thought this was a problem with just Firefox but then I realized that I ran into the same difficulty with Chrome and IE. Realizing this, I uninstalled and reinstalled Flash but it did not help. It only becomes a problem after several minutes of use. So for example, I can watch YouTube videos fine, but when I try to do something like play any old Flash game online or watch a longer video from somewhere like Hulu, or ABC.com, the image (whether it be a game or video) freezes and only loads a frame every few seconds whereas the sound continues normally. How can I fix this problem?
You may need to know more but I am running Windows XP with 512 MB of memory.