Invoice System written in C#

I need a simple invoicing system written as a windows application using C# and Microsoft.net. It will be an open item AR system. That means when a customer makes a payment it will need to be applied against a chosen invoice instead of just a running balance. I have the SQL script to create the tables already done. I also have a start on a Crystal Reports .rpt file for the layout of the invoice. Requirements: SQL Server 6.5 C# Very well commented - I plan to do the maintenance myself. Tables: Customer, InvoiceHeader, InvoiceDetail, Payments, User Screens:System Login, Add/Edit Customer, Add/Edit Invoice with invoice detail shown on same screen. Enter payment & select invoice to apply. Reports: Invoice, List of Outstanding invoices with filter on customer. ## Deliverables 1) Complete and fully-functional working program(s) in executable form as well as complete source code of all work done. 2) Installation package that will install the software (in ready-to-run condition) on the platform(s) specified in this bid request. 3) Complete ownership and distribution copyrights to all work purchased. ## Platform Windows 2000 and Windows XP