convert tab-delimited text file to XML based on a schema

I have a tab-delimited text file for a client that is filled with data.  A customer gave us an .XSD file for the schema of an XML file.  They want us to convert the tab-delimited data text file to an XML file based on the schema they gave us.  And of course, the schema has extra field names, and some of them are different than ours.

How can we do this?  Is there an open-source solution?  We are VB.NET/SQL programmers here.  We just want to take the text file we normally send them and convert it to an XML file based on the schema they gave us.  I'm kind of new to XML! :)