installing MSDE

Hi:
I'm just getting started with ASP.net and am trying to install MSDE. I am getting the error message : Instance specified name is invalid.
I have followed the directions in the downloadpage. Any help??

Thanks
Crystal.How are you installing it?|||Do you have another version of SQL Server running, i.e. 7.0? You may not be able to install MSDE with MSSQL7 running.