It depends on the bitrate. Some videos with the higher bitrate will lag and stutter, while the lower bitrates will play just fine.
I don't want to put anymore money into the computer. I decided to recover my P4 with 768MB of DDR RAM with a motherboard from emachines. Then I threw in my 8800GT, and before I could do that, I recently spent $30 on a Cooler Master PSU.
For those that didn't know, it was because of this emachines computer that I joined this forum.
My first post.