I think the motherboard model you meant to post is the MSI KT4V, not KTV4. Also, just because the motherboard is only seeing half doesn't mean there is anything wrong with the memory stick. More than likely, it's just not compatible with your mobo.
Do you have more than one stick of PC2700, or is the 512MB all that you have?
The best way to tell if a memory chip is faulty is to try it in another mobo. In the future, make sure the brand that you buy guarantees compatibility. Crucial and Micron are two reputable brands that will do this (of course, there are others).
~cdogg
[tab]"The secret to creativity is knowing how to hide your sources"
[tab][tab]- A. Einstein