How to show long navigation list horizontally?

We have a screen as below that has a long left navigation list that spans the whole height of the page and is scrollable (a lot of rows).

We also have an info panel that is basically tabular data. We want to show more columns but are basically horizontally constrained without moving the left navigation somewhere.

mockup

download bmml source – Wireframes created with Balsamiq Mockups

The obvious way is to move the left navigation to the top or bottom of the page, or perhaps even making it collapsible. If we want to avoid a collapsible navigation, I'm not quite sure about the usability of a scrollable horizontal navigation list.

mockup

download bmml source