Well, you said you were upgrading to 2008, so I assumed… Me-Bad!
The bad news is: (From a note on StackExchange)
SQL Server 2000 is not supported on Windows Server 2008 . If you simply must run it, I suggest building a VM with Windows Server 2003 and installing SQL 2000 on that instead. If you mess up your Windows Server 2008 , don’t go crying to Microsoft. They will not be able to help you .Sep 15, 2012
Now, with that said. If you need a FULL SQL server, you would have to buy it. But, MS has an Express version that handles most small tasks. Per MS:
Microsoft SQL Server Express is a version of Microsoft’s SQL Server relational database management system that is free to download, distribute and use. It comprises a database specifically targeted for embedded and smaller-scale applications.
It is free and easy to download from their site. I guess your choices are move back to Windows Server 2003 or either install the 2008 Express version for free or purchase a newer SQL Server version.
Hope that helps…