>ProductLevel = RTM
>
>Which is meaningless.

Why? It means that you don't have any service packs installed.

>Even if I know which service pack I have, there seems to be know way of knowing if I have all patches that have been released since that service pack.

I'm not sure what you mean. As I mentioned before, SP4 is the latest one. All servise packs are cumulative so you've to install only the latest one.