I have installed the wrong version of Small Business Server on our Server. I've installed SBS 4.0 5 user and upgraded it to SBS 4.5. However, we also have SBS 4.0 25 user which is what I originally thought I was installing.

How can I reinstall SBS 4.0 (the 25 user one) when it states that a newer version already exisits (SBS 4.5), without wiping the disk clean and starting from scratch?

TIA