JBS is pretty close.... If you keep you temp space clear of cookies and the fun different unknown downloads we all get, then things work faster. Because of cookies and site info that gets tied to all of our computers it chews up ram and ram is where your vid's download and run, so short answer keep your memory clean and clear by emptying your Temp files and cookie files regularly.
I'm sure there is some one on here with more info than me, but thats my suggestion.