Hi Everyone,

I just entered the world of Linux and Ubuntu is my first stop. It's been about 3 hours since I installed it on a old PC - Pentium 4, 1gb DDR2 533 ram (Dell Optiplex GX620). I manually installed a ATI Radeon 6450 and managed to get its driver to work (or that's what I believe).

My problem, as stated in the title, is when I watch YouTube videos in HD quality (on FireFox), the video is not watchable - very choppy and the audio lags. At first I thought I didn't install my video card driver properly, but when I play a HD movie file from HDD, the quality is as good as it gets. Is this a problem with the Adobe Flash plugin I downloaded from the Ubuntu Software Center?

I briefly Googled this problem and it seems like a common one but I can not find a solution. If anyone here can give me some advice, I would greatly appreciate it.

Thank you for your patience!