When I was trying to install MOSS 2007 on Windows Server 2008 I ran into an error stating that there is a known compatibility issue with this version and that I should install it with the latest service pack. After a quick search I ran into a blogpost from Matt Hester who ran into the same problem. He posted a really good screencast about installing MOSS 2007 on Windows Server 2008.
The solution is really simple. You just have to slipstream WSS 3.0 SP1 and MOSS 2007 SP1 into the install CD. The first step you take is copying the install CD onto your local hard drive. After you have done that you can download the service packs from the Microsoft website. When the downloads are finished you run both of the setups with the parameter /extract:[pathtoinstallcd] (replace [pathtoinstallcd] with the full path to the location you copied your MOSS 2007 install CD).
If you executed the steps correctly you can now run the setup and start installing MOSS 2007.