Will not work for Exchange 2007 but you can administer Exchange 2003, you will need to go into IIS and select what flavor of .NET you want it to use. It will not work until you tell IIS on the OWAAdmin Virtual Folder to use .NET 2.0...
For Exchange 2007 OWA...http://technet.microsoft.com/en-us/library/aa996373(EXCHG.80).aspx