Well, if you so desperatelly need to know, maybe reading a documentation would not be a bad thing to do. :-)

Anyway, Joomla meta tags can be overriden in JoomSEF Metabot (plugin) as already said.
It is located in list of installed Joomla plugins, among system plugins - in joomla 1.5 the exact name is "System - ARTIO JoomSEF".

Jan,
FYI, the information we need is not found in your documentation, at least that we could find.

With your post here it was much easier for us to find the plugin in question. However, we are not getting the results we need with the settings at our disposal. Our JoomSEF title and meta tags are being overwritten by the Joomla title tags.

Here's what we have selected:
Enable MetaData generation: YES
Prefer JoomSEF titles: YES

So, what's wrong? How do we get your extension to work and get our meta data showing properly?

Thanks.
Kathy