is 256mb low for video memory on a brand new computer? how will it affect the computer?
Video memory is far less important than the actual GPU in the computer. Most pre-built computers come with either integrated graphics or a weak video card, both of which are only okay for light gaming (such as Warcraft II) and movies and the like. They may also eat RAM to use as video memory. So it really depends on what you use the computer for, and the GPU in question.
Video memory is like RAM in that more is better, but is not the same thing. 256MB video memory is pretty much average, but there are cards with 512MB if you feel the need for them.
depends on what you plan on doing. There are cards with video memory all the way up to 1mb. Generally more is better, but not always. There are cards with less memory and better performance than higher capacity cards. Read the reviews.