Windows 2008 does not support installation of Share point Server 2007 without Office/WSS Service pack 1. Therefore when you try to install share point setup on Windows 2008 machine it will give you an error that service pack is required to run this installation.
In order to run installation on windows 2008 machine you need to perform following set of activities.
First download WSS Service Pack 1 and Office Sharepoint Server 2007 Service Pak 1 from Microsoft site.
Copy all files from installation CD to local disk.
Open command prompt and navigate to folder where you have downloaded service pack1 for WSS and Office server and run following commands
Copy all files you extracted in last step i.e. C:\WSSP1 and C:\MOSSSP1 to Updates folder of Sharepoint installation (at local disk)
Now run sharepoint setup from your installation files in your hardisk. It should run properly.
Basically Windows 2008 require you to install Sharepoint setup file with SP1. Sharepoint setup looks in updates folder and applys those updates with installation so as we copied extracted files of SP1 in updates folder of shrepoint setup it will automatically deploy those files and will not give any error.