Although SQL Server 2000 is not supported at all now and MSFT does not support 2000 on a windows server 2008 or 2008 R2 environment, you can install SQL Server 2000 on one of those servers.

I think the issue you were running into was related more to installing a developers edition onto a server that already had a 2005 instance that was either standard or enterprise.

You might reverse the installation process and install the MSDE version first and then reinstall the 2005 instance.

One thing you may run into though are problems with mail and some ODBC connections, which you will have to work around.

Bottom Line. Even though it IS possible to install on a 2008 server, it is not optimal and you are asking for anomalies (also known as gremlins) to pop up, especially if your Windows server is also 64bit.

I would NOT do this in a production environment. but if you have a test environment to play with then try it out.

Good Luck