I know I may be late, but I just ran into it. In an application of mine I use the standard ADO.NET persistence format for saving data. I have got quite some files that I now need to convert into the new msdata-xml format supported by .NET 4.0. However I found a very helpful tool to speed this up It is called XSD: http://msdn.microsoft.com/en-us/library/x6c1kb0s(VS.80).aspx
If you specify the command line:
Xsd will generate a new schema consisting of 4 *.xsd files for you, which you can use to import the old data files into .NET 4.0 Datasets. This is done by loading the XSD generated schema before you load the file into the dataset.
Of course, the XDR files you put in should have been created from a previous version of the Dataset.
I know, there will be quite some additional tasks to get this working in a complete application, but consider it as a good start.