Anything less than 1GHz for CPU speed will slow it down
tremedously... even with loads of RAM. Video processing is still
very much dependent on processor speed rather than the amount of
RAM you have.
On my P3 600MHz... with 512MB of RAM... just need to load a few
Youtube videos to kill it... simple as that.
Another thing to note... if you visit Ajax webbies with that
kind of processor, be prepared that it will slow to a crawl. On the
client side, it's more interactive, but this also means more
processing power on the client side.